Even if id did work, it's just bound to be slower that's all.. Imagine a spider getting healed ~40 every 2 seconds (healing spring) and you stealing ?? (a lot less) health every attack. Stalemate...
well, then we'll just have to pay them off so they don't use healing spring.
While your not useing that life stealing elite you'll be useing another skill thats aoe if there is one.
Plus they attack about once ervy 1 second. they get healed once every 2 seconds. You'll still deal more damage than they get healed. Also you can seperate them so healing spring is less effictive.