For healers? In general I'd like healing tools to be more useful a small overhaul in general on healers would be a welcome change.
Sage? I just want more abilities tied to kardia usage (such as a aoe kardia, or allowing kardia to grant barriers ect). just more cooldowns around the kardia design would be intresting.
WMH, Mainly visual reworks, longer cast times for spells would be nice

Other jobs?
I hope Paladin gets a mini rework (6.3 was a thing but theirs still issues0, I think it's current design needs a lot of tuning but divine might works fine, but a lot of abilities dont really feel like they serve much purpose such as goring or Fof they could also merge some abilities at this point, fixing up cover/clemency/shield bash to all be more useful would also be neat.
I also hope Dark knight gets a major rework. I don't really know where to start though.