Ok, let me be first to break this down...
Vonderam, i don't see why its such a big deal, but since that condition doesn't affect the net effect it was intended for if pulled of (and its not hard to pull off) then its ok.
Miffy, i don't think removal is a good idea. its a unique skill and it gets a good niche. i can only imagine a bunch of key lvl 1 cards in horizons making this nerf that necessary. (also, back to spamming undines, yay!)
Fellana, again doesn't seem like a good idea, but again there may be very key grims you're looking at (or something that can too easily make use of a Fellana opening) that you're worried about, so ok.
Janus, nerf well deserved.