If we're talking combat reworks, the one thing I'd definitely like to see is the Black Mage "Banishment" ultimate either heavily reworked or completely replaced.
As it is it's the worst in the game by far, IMO: at best hardly ever useful, at worst literally game-breaking. (Now, maybe all its glitches have finally been fixed, but having once had that thing ruin a run of the underwater temple, you can maybe understand why I'm reluctant to try it again.)
The only time that power IS ever useful, ironically, is in its least common case---against "constructs and ethereals" (of which there don't seem to be all that many in the game, and which it's impossible to tell in the middle of combat whether what you're facing counts as that or not), where it serves instead as a simple damage nuke.
Personally, I'd rather just see the whole "banishing" aspect of the power removed entirely, and simply change it into a heavy AOE damage spell, possibly with some added debuff or stun for good measure, thus making it sort of the magical analogue to the Thief's "Assassinate" ultimate.