well tanks are designed in a way that damage helps them tank, be it grab enmity or for self healing, attack power based moves,
they could do healers like they did tanks, just be careful of the end result, make mind and piety average healing potency and cs now swaps healing potency with attack power. As someone who saw the vit changes hurt self mitigation and enmity as a whole, i dont think thats the solution you want, but it could happen to force healers to heal youre not a dps. That being said...
the meta will probably have to shift in some form or another. to be fair a 4th healer or tank probably will not change things until they do