warlocks, mana, and health

(This is just a passing thought)

How cool would it be if warlock spells cost not just mana, but the same amount of health? Thus Curse of Agony might cost 100 mana and 100 health, and similarly for all other spells. Toss in a couple of talents to adjust the ratio involved (eg. 40%/60% or 60%/40%), and rebalance all the base mana costs to suit, and you've got an interesting game mechanic which sets the lock apart from other spell casters.