Well, Selene is a very underrated faerie. You also got a Silence and a Raid-wide Erase, and of course a bit of speed. True, Rouse will only enhance her healing, but 40% Healing bonus is pretty good on it's own. And if you needed another reason to keep her on Obey.... you can force cures from her when the hp threshhold isn't there, for when your anticipating a hit like you'd pre-cure anything else.