FoF on the spirits would be fun for sure, but I've got the feeling that we'll see a nerf pretty soon. (probably op in this state)
Would be nice if they could fix the whole SEF targeting issue as well, I'm curious if they want the spirits to be targetable or not.
My guess is that they want them to be targettable, it'd get changed/whined about pretty fast if they weren't on live as there'd be no way of stopping the spirits hitting you for ~11k every .x seconds. In PvE it won't make much of a difference if they are or not.