A bunch of disorganized opinions, mostly about healers since that's the role I play the most:

Scholar and Summoner are a mess thematically, I'm assuming because they've gone through so many reworks.

Like the story and art design tells you Summoner is supposed to be a pet/summons class but in reality the summons are purely cosmetic, and it's actually just a bog-standard ranged magic thrower with a fairly rigid rotation. That's kind of disappointing really, considering the other ranged DPS classes have their own interesting gimmick.

Likewise SCH is called Scholar but the skills don't particularly reflect this theme, and in fact one of your most used skills (Art of War) has you running into the fray to do a very unga-bunga feeling ground pound.

I actually really like where Astrologian is at complexity-wise. From what I hear it used to be much more complicated and old AST players hate the change but for me AST as it is now hits a sweet spot in being busy but not so busy that it's overwhelming. Some button bloat issues aside (there's no reason for Draw/Play to be separate buttons) Astrologian is a blast to play once you get into the groove.

I don't think WHM/SCH/AST's Tier I and II GCD heals should be separate. There's no reason to ever use Cure I once you get Cure II (etc) but the game kinda tries to mislead you into thinking you should still keep it on your hotbar.

More generally, I don't like that many jobs split their basic attack combo into many buttons. I recently got into Frontlines, PvP combines these combos into one button and it works completely fine! Spreading it across three buttons is pointless.

Oh and this one is even more subjective than the rest: I think Peloton should be a healer role ability instead of ranged physical DPS. A support skill like that just feels more at home in a healer's kit, idk.

And I'd love for healers to get more crowd control options (eg WHM's Holy stun). Healers in this game don't really need to heal a lot of the time, but instead of defaulting to being "discount DPS" it feels more fitting to give healers more options to indirectly contribute to the fight. Doesn't have to be as punchy as Holy's AoE stun but something like applying vulnerability or slow would be nice.

(I suppose technically healers do have Repose. But I've never found a use case for it in dungeons since it has a long cast time and the effect dispels upon taking damage.)