Probably too much change for the game given how mature it is. But I do think that the old tank / healer / damage roles will become obsolete in future RPG / MMOs. You can do utility roles without having the holy trinity and it makes things easier for matchmaking. Diablo already has boss battles and party co-op without the holy trinity.
Personally, I prefer dodge / parry / block / shield mechanics to damage sponge HP ones. The Shadow of Mordor series did an amazing job of making fight mechanics utilizing that very fluid with a high degree of skill growth allowed.