Ast is fundamentally flawed, and will break the healer balance forever until they make it a different type of healer instead of a copy of a white mage that can also use the scholar shielding tools. There's just no way for it to ever be balanced when it does the same things the other healers do and has cards.

Maybe in the expansion where we go into space and they decide to make a new tank and healer to get DPS balance right things will get fixed. But healers are gonna be in a weird place forever until things change on a fundamental level.