This is an amazing idea, i love the fact that this Healer can use Buff/Debuffs as his advantage, it can become the only Healer with a actual rotation likes DPSes, and he needs to be very precise with his team to get the maximum from most of his spells (Extend and Time Slip).

Again, i love this idea, but i think a 4th Healer is too much right now, and to balance everything of his spells it's going to be a nightmare (as we see with AST, balancing Healers is quite hard).
But if any day it comes in the game, be sure i'll play it right after it dropps !