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.
Broken Base: On the Radiant Mythology side, people are split on who the best healers are. The arguments usually are whether or not Estelle, Mint, or Tear is the best healer, nevermind the fact that the above three are only a few of the healers in game.
In general bringing up ideal parties is treading on Flame Bait.
Tier-Induced Scrappy: Since each game has such a large amount of characters, some are not very useful.
Chat is one because she has four artes, none of which are really strong. The only useful thing about her is her ability to spam attacks in Radiant Drive.
Asch too is one mainly because he's a Master of None. He's a Magic Knight sure but he has no highend spells, no healing, and he's a bit clunky. Luke has most of his artes but is stronger, Jade is a better spellcaster, and Van is a Magic Knight with much better artes and stats.
Judith, which is sad because it's only because her artes were implemented in weirdly and she can't combo very well.
Annie, mainly because her fighting style is by making glyphs that either buff or heal...which is a issue when you have a 3D style that makes it IMPOSSIBLE to use it.
Between the Descender's classes themselves, Thief and Archer. Especially Archer post-RM2 due to Nerf.