I do think Gravity could more closely resemble the classic spells.
It wouldn't need to reduce hp by half, just scale with hp, inversely to Essential Dignity.
Like, base 100 potency +20 for each 10% hp target has, to a maximum of 300 potency when target is at full hp.

This would make it different from all the other aoe abilities, instead of returns diminishing with more targets, it would diminish with repetition, meaning after so many uses it's effectiveness would plummet. As a healer, this is fitting, some burst aoe damage at the start of a pull, then the for can finish it off and you can heal.