I'd still love to see something more inventive that creates incentive to stack VIT, but it's probably more effort than SE is willing to put in.

Warrior - increasing dmg the further from max hp you are. Maybe Fell cleave/inner beast scale based on HP missing?
DRK - One or two of their damaging abilities could consume their own hit points to use?
Pld - uhh... i dunno, they'd probably still be screwed! Or maybe the new Paladin Relic could be something like the Atma weapon from previous FFs. the more hp you have, the more dmg it does.