Uh, hard to rate this card, because it totally depends on what powers/bodies you want to seal... considering it seals all of your own passives as well, I wouldnt abuse it unless absolutely necessary...
However, I wouldnt give it too much credit, because the coming series has a Gardevoir ex that can passively seal an opponent's passive ability once a turn - that, IMO is much more managable as it has no negative side effects.
Anyway, I'll give it a range of scores between 3 to 7 out of 10, depending on how and when you use it, and of course, depends on what decks you use.