Ahh game balance

Where heals for 12% of someone's health at a cost of 12% of her base mana is toxic and she has to by a chalice to be viable but where being able to completely negate an entire team's burst and is technically purchasable by anyone is nice and healthy for the game. Or where champs get their kits ruined because is in the game, but the real problem of DFG is allowed to stay put.

BTW, why not make AB a flat percentage heal? It costs X% of her max mana and in return she gives them back Y% of their missing (or max) health. Make it more mana efficient as she levels it up, but keep the heal amount the same.