Why do the X-Wings in these books use their missiles so much more often than in the rest of the Expanded Universe (or the films for that matter)? They seem incredibly powerful and TIE Fighters have absolutely no defence against them. For that matter if X-Wings are routinely equipped with such powerful weapons why do the Imperials ever risk capital ships against them? Granted a Star Destroyer won't (usually) have much to fear from a single squadron but smaller cruisers and frigates would be sitting ducks.
Depending on the Writer? The power of Jedi throughout the Expanded Universe isn't exactly consistent either, for example, so inconsistencies with military technology and tactics aren't a tremendous stretch. It could also be that because the squadrons in these books are the elite, and they are better at maintaining the necessary unit cohesion for anti-capital ship torpedo salvos even in the thick of battle.
The risk posed to capital ships by missile- and torpedo-equipped fighters is always high in the entire universe, it's just the level of said risk that varies according to whoever's writing. It gets to the point that the imperials eventually design and build a capital ship that has no purpose other than defending other capital ships against fighters (the Lancer frigate, entirely devoid of heavy weapons but with a crapload of anti-starfighter laser guns). And the games turn the whole concept up to eleven... but they're probably non-canon, otherwise it isn't really explainable why other works don't feature entire wings of small craft carrying heavy rockets or space bombs.
The common usage of missiles compared to the films may have something to do with logistics. That is, the New Republic has an easier time producing and delivering photon torpedoes than the Rebel Alliance, so pilots don't have to be quite so frugal with them.
Using torpedoes against TIE fighters makes sense when there are other objectives to be met. Why waste the time dogfighting a faster, more maneuverable vehicle when you can just 'fire and forget' a torpedo that will track and destroy your enemy while you go back to saving your wingmate?
But that's part of the problem. X-Wing's already had a significant edge over TIE Figthers in durability and firepower but not so significant TIE's didn't prove a bit of a threat. Giving X-Wing's a large missile payload as well makes them so clearly superior it stretches belief that the Empire would continue using TIE's at all with - even a We Have ReservesZerg Rush philosophy has limits. From a storytelling point of view it is a problem too since it diminishes the success of the X-Wing pilots - they are flying such clearly superior weapons that the odds are always going to be heavily in their favour.
I think that's somewhat intentional. They don't deny that the X-Wings are insanely superior to their Imperial equivalents and it is repeatedly said both in this series and others that it was one of the largest contributors to the Rebels winning - especially highlighted in the 8th book where they talk about the TIE Defenders and how those would've changed the odds significantly at a lot of major engagements. There's also some hints that the Empire's view is beginning to change - but not drastically so. The other EU books never really picked up on that point, though, so you see a bit of discontinuity there (there were some hints by the NJO series that changes had been made, finally). Keep in mind that new designs, today, take decades to go from theoretical to prototype to deployed (the requirements for the yet-to-be deployed F-35 were written in the early-to-mid 90s) and that by Endor, only 5 years had passed since the start of the war and 8 by Rogue Squadron. On a side note, the games suggest that the Rebels considered the standard to be that one X Wing could fight three TIE fighters evenly so Zerg Rush tactics would still be valid. As for the reason they use missiles? Because it limited the risk threat by reducing enemy counts sooner rather than later and it may be a reflection of real world tactics - fighters are often equipped with both missiles and machine guns and standard practice is to attack with missiles first (and at range) and use the machine gun when you have to.
But while missiles might be the standard weapon in real life air combat the original Star Wars films clearly show lasers as being the universal starfighter weapon at Yavin and Endor. In fact even larger ships don't seem to use them; Star Destroyers fire only turbolasers. Missiles are used in the movies but only against large 'stationary' targets like the Death Star reactor. They aren't used ship to ship at all which makes the sudden shift to a missile dominant strategy pretty jarring. The other issue with using a real life missile system is that it means TIE Fighters are for all intents and purposes unarmed at range, which stretches the quality gap a bit too far to be plausible. X-Wings might be intentionally better craft but still.
IIRC according to the EU, at Yavin the fighters only carried 2 torpedoes each, due to having a limited supply at the Yavin Base. At Endor, it's likely that the fighters used their missles engaging the TIE Fighters and the various capital ships, which explains why Lando takes so few fighters into the Death Star with him: they are the ships that still had torpedoes at that point in the battle. As for the TI Es being unarmed at range, that's why the Empire uses the Zerg Rush tactic: keep sending fighters until the Rebels are overwhelmed, since the fighters carry only a limited number of torpedoes. Once they lose that advantage, it comes down to a laser battle, in which the TIE fighters are faster and more maneuverable than the X-Wings. And since the Empire had the advantage of clone pilots, they could replenish their ranks quicker and easier than the Rebels could.
According to Corran Horn in "I, Jedi," Rogue Squadron has no qualms about using proton torpedoes, but there are other fighter pilots who view it as overkill. IMO this might be because the Rogues being an elite unit would have no problem getting resupplied, whereas a lower level unit commander might get chewed out for wasting a valuable torpedo on a lousy TIE.
"even a We Have Reserves Zerg Rush philosophy has limits". No it doesn't - not at the levels the Empire were using it back when they were big and powerful. The Rebellion had to make do with a few squadrons of vastly superior fighters, while the Empire had - very literally - thousands of TI Es for every one X-Wing. There are levels of overkill that no heroic willpower can beat; the Empire knew this, and would indeed have very easily won from sheer numbers had it not displayed extreme stupidity in the design of one tiny little detail in their super space station.
Actually that's a debatable. The exact strength of Imperial forces varies Depending on the Writer but the most common statistic I've seen for Imperial Star Destroyers is a figure of about 25,000. That sounds a lot and it is... but then remember that the Empire has on the order of 10,000 sectors (population of a sector obviously varies but the Imperial Remnant had "over a thousand inhabited systems" when it was reduced to just 8 sectors according to Spectre of the Past.) That means the Empire has an average of 25 Star Destroyers to guard a stretch of space that might contain over a hundred inhabited planets. In other words even at its peak the Empire was very thinly stretched because it literally had to be strong everywhere at the same time while the Rebels could pick and choose their targets.
Why does Iella Wessiri always forget that blasters have a stun setting only when she's forced to shoot somebody who she doesn't want to die? On two different occasions she kills somebody she blatantly wanted to take alive, despite being a vocal proponent of using the stun setting at other times.
In Mercy Kill, its revealed Face operates the Wraiths on a very extreme 'need to know' basis. To the extent they only know their own parts of the plan which leads to 'better operation security and a lot of temporarily confused Wraiths'. How can confused Wraiths in a middle of an operation be a good thing and not lead to unnecessary casualties?