It's not completely useless in endgame, if theres a lot of damage going about and you need lustrates, indomndibility to keep everyone up those extra stacks on aetherflow outweigh the healing potency of your faerie, in context not in numbers.

But it is the oh shit button of oh shit buttons and the 20% healing potency is overall meh. It needs to be changed so at the very least your faerie comes back after the 30 seconds automatically and increase the healing potency or add a crit % increase (play to us scholar egos)