These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Dot A 2
Acceptable Targets: The playerbase, like all MOBAs, have a seething hatred for all people Brazilian or Russian due to a Vocal Minority who troll games going "Huehuehue" or going onto the American servers and demanding them to speak Russian.
Base Breaker: Jakiro used to be a relatively mediocre nuker with a nice passive and pretty good at pushing, but overlooked among better options. Then his Ice Path was changed to be one of the best stuns in the game, while also dealing damage and being cheap in mana. Jakiro overnight went from rarely ever picked to a staple, and drew cries of being a game breaker.
Dragon Knight gets some flack for having the longest Level 1 stun spell in the game. The trade off is that it's melee range until level 6, but it can chain stun with something else like the above Jakiro and turn a tough lane into a complete massacre.
Invoker: One of the most powerful heroes in the game whose power justifies his high skill ceiling or an overcomplicated Jack-of-All-Stats? The debate comes down to the idea that Invoker is as strong as the player behind him: He has ten amazing spells but you need to be able to combo them properly and Invoke them quickly for it to pay off.
Fell out of favor when 6.75 nerfed him after the second International. He took too long to come online compared to more focused gankers and teamfight heroes who became useful far sooner. He's started to come back into favor with 6.79, which allowed him to Invoke two spells with one level of Invoke. It makes his skill builds more flexible by letting you skip Invoke at level 7 and gives more option for laning-phase plays. That as well as the craze of "Build Hand of Midas on everything" letting him get to his magical level 12-13 much faster.
There's also the classic MOBA debate of whether there should be a surrender option. The closest thing to it is the "Game is now safe to leave" feature that kicks in when someone leaves the game. The side favoring a proper surrender option says it's better to just surrender to an assured loss and move on, while the other says the option would ruin the game's sense of competitiveness and make the potential for comebacks even worse than it currently is.
In April, Valve introduced a mute system where players above a certain report threshold lose the ability to communicate with the rest of their team. The main dev site was embroiled in a flame war. It was remedied when Valve let them use the Chat Wheel to convey basic ideas such as "Missing Mid" into chat and limited the number of pings they could use in a row (usually out of spite to the mute).
Character Tiers: While there isn't exactly an "Official" tier list, there is general consensus on the quality of most heroes. Cries of anguish from teammates when they see someone pick Meepo in a pub is the most evident example of this.
It's worth noting that these can vary widely depending on the latest patch, region, skill level, and even individual games as a draft unfolds. In the Competitive scene there are about 10-15 top picks at any one time, a wider roster of about 30-50 that are picked up often but not always, 20-30 who will are picked rarely, and at least 10-15 heroes are seen as inferior to other options or only useful in gimmicky drafts.
Complacent Gaming Syndrome: Done by the Bots. Depending on the AI difficulty levels, after Practicing with Bots for a few times, you may notice that the AI will generally pick only a certain subset of heroes and never experiment with other heroes. This may reflect how real-life players stick to their strongest heroes, but it's more that they're limited by the fact the "Bot Guy" who coded the bots had long since left the Dota 2 team for other projects at Valve and never coded bots for more complicated heroes.
Bots are generally seen as useless beyond a certain level of mechanical skill anyways, as they are unable to react to the subtle nuances of the game that humans do. There's a few patches floating around to remedy this for those who want to avoid the notorious player base.
There's also something to be said about real players who go for the same item builds and skill builds every time they play a hero, disregarding whenever a different build would far better suit the match at hand.
Crack Pairing: Technically any pairing outside those characters who explicitly are tied together; no hero has a response to every other hero.
Faceless Void and Phantom Assassin area moderately popular couple, for whatever reason. Perhaps because they're both naturally evasive?
Phantom Assassin and Omniknight are another popular pairing, particularly in the Russian fanbase.
Fanarts also seem to like pairing Sven with Rylai and the reasoning may be a little more off. They can't be the only blue-colored heroes in the game.
Ensemble Darkhorse: Juggernaut, Axe, Nature's Prophet, Death Prophet, Tusk, Lina and Storm Spirit all have announcer packs. While every hero has their fans, some other universally liked heroes include Rubick and Axe.
The Goblin Techies, a hero as yet unreleased in the sequel, are the most anticipated and demanded heroes in the fanbase. "Added Techies", is a fairly common joke patch note in the fandom. Though many others are just a quick to point out that "Give Techies" is more of a joke than a genuine desire for their mines hidden everywhere on the map.
Game Breaker: As balance patches come and go, sometimes what seems like a small change can hugely affect the overall prowess of heroes, especially in the competitive scene where skill levels and team compositions can magnify specific advantages. Other heroes will become popular for a month or two as they seem unstoppable, then gradually fade away again as the metagame adapts to their counters. This is standard practice for Dota, and has been the case for years.
Some heroes are more than fad-picks in the competitive scene, though, and tend to be dealt with more thoroughly in the balance patches. Dark Seer, Batrider and Io were all staple picks to most teams and near consistently banned in the first ban phase of the majority of high-tier pro games. Alchemist was also a dominating pick during TI 3. When 6.79 came out, they all immediately fell off in favor of heroes like Lich, Luna, or Viper.
Before the Adition of Ember Spirit and Legion Commander, Phantom Lancer was the best carry, highly capable of escapes, having a stealth and a slow, compared to more vulnerable yet less powerful Carries, and exploited that mana burn on all illusions is the same as that on the main hero, to deal utterly insane amounts of damage. Thankfully, with the adition of the two aforementioned heroes, Ember Spirit being able to hit everyone with an attack that has all his modifiers, including Cleave, to cut massive chunks of Phantom Lancer's health to bits and turn him back into one hero, and Legion Commander exploiting Phantom Lancer's Death of a Thousand Cuts to rapidly heal while dealing large chunks of damage, beating PL's hordes through sheer Attrition.
Most Annoying Sound: Just about anything Storm Spirit does. Imagine this going on for over an hour: "I'm over here!", "BLOOOOW THE MAN DOWN!", "Touche!", "ZAAAAAP!", "BLOW THE MAN DOWN!", "Puddin pop!", "I'm over here!" "Where's the party?" "Who's that handsome devil?" "I'm over here!" "Where's the party?" "ZAAAAAAP!" "I'm over here!" "Over here now!" "Where's the party?" "ZAAAAAAAAP!". On the other hand, Storm Spirit has quite the sizable fandom who considers his voice to be a strong contender for Most Wonderful Sound.
The same cannot be said for Windrunner, whose quotes include such nuggets of banality as "You hit... a girl!" "Why do you hate gingers so?" "Bury me... beneath the tree" "Ooh, now I get to shoot stuff!" and of course "Your tiny featherless arrows can't hurt me, Sniper!"
Pudge. The main problem is that his ult is heard globally, so even when nothing may be happening in your section of the map, you're going to be hearing "Fresh meat!" over and over again when the Pudge player is particularly good.
A teammate spamming pings on top of you and constantly using the "Well Played!" quick-chat whenever you make a mistake. Or do something they perceive as a mistake. Or did not join them in their mistake and made them look like the only idiot for dying. Or died saving their ass but it looks like you feeding.
Hearing the slot machine make Jackpot sounds when you manage the amazing skillshot of a 4X Multicast on your Fireblast or Ignite as Ogre Magi.
Phoenix doing a triumphant screech once the battle begins and again, when/if his team is victorious.
Narm / Narm Charm: Some of the heroes have really bad voice work. Luna in particular has become memetic for this gem.
Rescued from the Scrappy Heap: Alchemist used to be rarely seen in matches due to a crippling reliance on farm, aided by the fact one of his skills does nothing but give him extra gold, and the fact that enemies could see how charged his stun was. However, thanks to 6.75's immense buffs to him, he became a much better hero all around. Considering that he was a Joke Character before said patch, that's saying something. He got nerfed 6.79 after being a little too popular at TI 3, but it's not to the point that he's unplayable. He just has to farm at least one health-giving item before he can get damage because his ult gives massive health regen instead of bonus health now.
Spirit Breaker received a massive buff in 6.75, causing him to go from barely seen in pubs to the local Game Breaker for how amazing he was at ganking. Nerfed in 6.79 so that his ult could be stopped while casting and he was put somewhere between back in the Scrappy Heap and balanced.
Naga Siren and Morphling, after being widely detested for being ubiquitous at The International 2012, suffered heavy nerfs in 6.75. However, they slowly worked their way back into the meta by the time of The International 2013 where they became crowd pleasers.
Lycanthrope was equally detested during The International 2012 but almost never seen during the tournament. Because he had an almost 100% Ban Rate across the event. He was given nerfs to where he snowballed the hardest: the jungle. His ability to jungle was crippled, and his reign of terror upon pub games ended. Now he is a really, really good pusher but not to obscene levels if you know how to handle him early in the game.
Heaven's Halberd, a decent mid-game item with evasion and the ability to Disarm a hero from attacking, has found a niche as a siutational support item for its utility in teamfights. It found this favor after Manta Style was changed to no longer dispel its Disarm. But because BKB still removes Disarm, it's lumped with Rod of Atos as "Support Items that sound amazing in theory but just come up to snuff in practice."
Sacred Cow: Comparing this game to another MOBA will get you obliterated on certain forums and imageboards. As can referring to it as a "MOBA" at all, as most fan prefer to just call it Dota.
Scrappy Mechanic: For new players; Creep Pulling can be a large hurdle to overcome when learning to play support heroes. You need to stack the creeps by taking their aggro and dragging them from their camp a few seconds before the "refresh" time of a new minute. If you do not do this and just pull a single creep camp in, it will push the lane out and make your lane partner unhappy.
For every discussion there is about adding Goblin Techies to the game, there will be a person who brings up finding a random Clarity/Salve/Iron Branch on the ground and dying to their mine trap when you try to investigate.
Evasion can be this in certain situations where a fairly straightforward encounter becomes equal parts confusing and frustrating. (Brewmaster's passive gives him natural evasions, while one of his skills adds more "miss Chance" on top of it, meaning Phantom Assassin basically never hit him when she normally could.)
Linken's Sphere can be one sometimes. Some abilities, such as line stuns (Jakiro's Ice Path for instance) will be blocked if targeted on the unit but work if they're targeted on the ground in a way that still hits them. This is a matter of no small annoyance, for both stunners and Linken's holders.
"Stop Having Fun" Guys: This is one of the worst games for this, practically being a Wretched Hive. Alleviated somewhat by the report system, which more often than not puts the worst offenders in a "Low Priority Queue" pool or gives them communication bans. LPQ matches them solely with other members of the pool, all rude and unpleasant in their own way, and you have to play five matches in it to get out. Communication bans ban them from using text or voice chat for a day or two.
Fans of the original game often react poorly to changes that deviate "too far" from how the original game was. Even something as simple as names and appearances, which often are changed for copyright reasons, cause backlash among veterans and newer fans alike. Examples that come to mind are Brewmaster (originally known as Pandaren Brewmaster) being turned from a standard Panda to a Red Panda, Doombringer having his name changed to Doom, and Bristleback having his name be Bristlebog during development But ultimately reverted. More recently Windrunner became Windranger, and Necrolyte to Necrophos. Skeleton King got an entire event and game mode based around his remake into Wraith King (Though that change seems to be recieved more postively due to Wraith King's copious amounts of ego and swagger). It seems that Blizzard has their finger on the lawsuit trigger the moment Valve slips up.
Patch 6.79. The changes to buybacks, the day and night cycle, courier, and certain changes to heroes did not rub well with more than a few fans. That mostly went away when the patch actually dropped, but more than a few people still wonder why Night Vision has to be near universally crap.
Averted with Storm Spirit's remodel. When it was initially discovered that he would receive a new model, the playerbase assumed the worst because they had grown fond of the originally derided design. When it was finally revealed though, the playerbase immediately changed its tone.
Tier-Induced Scrappy: Quite a few heroes are innately unbalanced in pub games, while others require massive amounts of skill to use effectively, rarely making their appearance in pub games simply because they're very difficult to use:
Meepo is a classic case of Difficult but Awesome; skilled Meepo players can reach the level cap and amass items long before any enemy carries are able to deal with them. The problem is that if only a single Meepo dies, all of them die, and illusion based heroes like Chaos Knight and Phantom Lancer can fill a similar role of swarming the enemy without being as vulnerable. Not helped when 6.79 patch initially looked like it would give him an interesting buff but turned out to mostly just make him worse at the time he's already bad.
Broodmother consistently had the lowest winrate in pubs and is almost completely ignored in pros simply because her spiderlings are free gold for anyone with Ao E nukes. Unlike other heroes with summons, who usually have one or two big strong summoned units, Broodmother relies on summoning a lot of very weak units and swarming heroes and structures with them. Rescued in 6.79 where her webs allow her to walk anywhere, and now she's got a much higher win rate than before.
Io was detested amongst western pro players for essentially being a necessary ban in most professional games. 6.79 took the hero out of favor when its Tether ability no longer stunned enemy units that crossed it. Instead it is a 100% movement and attack speed slow, which means heroes can still retaliate with spells and item abilities.
Ursa is something of a one trick pony; he can apply massive physical burst but can be kited around easily. But if he has a Blink Dagger and is against particularly dim-witted players, he's a Lightning Bruiser with no equal.
Huskar was detested in 6.78 after his Berserker's Blood was changed to give him more Magic Resistance the less health he had. When combined with Ghost Scepter, which has an active that makes you immune to physical damage, he literally could not die unless you had Pure Damage which can be hard to come by, especially if he picks his hero after your team picked theirs. 6.79 made him almost instantly forgotten when he could no longer cast his Flaming Spears during Ghost Scepter's active buff, and is now a Scrappy in the lower tiers.
Nature's Prophet: if you ever turn your back on a tower for a minute, you can be sure that he will be applying pressure. Not helped by Admiral Bulldog of Alliance making the hero not simply popular, but near ubiquitous in pub games. If you see a Prophet in a pub, he will go to jungle, rush Hand of Midas, and then split push. He might go Orchid, Shadow Blade, Dagon or Necronomicon afterwards or use his ult well or poorly, but he will almost always go Jungle for his Midas regardless of how weak it makes his team's lanes.
Spirit Breaker during the 6.78 patch was broken in pubs because if his Charge connected it was a guaranteed 500~ magical damage as well as many infuriating seconds of being stunned. However, after his 6.79 nerf (Nether strike now uses cast animation that lacks magic immunity, along with a reduced base attack speed), his win rate plummeted to manageable levels.
Vanguard as an item is generally viewed as inferior to a Mekanasm. Vanguard is more effective for damage reduction, but quickly falls off in effectiveness, doesn't offer anything to teammates, and generally isn't worth the investment. These days, it's seen as a situational item at best for heroes with damage return passives, like Axe and Spectre, or squishy agility carries in need of some quick health, such as Phantom Lancer and Riki.
Storm Spirit's original model was changed from the Pandaren for Dota 1 into a rather weird looking human. His teeth looked like they weren't connected to his chest. His new model from the Spirit Update averts this.