Gravity shield completely stops some decks. For example, mono aether dimensional shields and phase dragons deck. Most decks, however, have some way of hitting it. A fair amount of decks have PC or some way of getting around shields (poison, momentum). The remaining decks have most of their creatures able to hit this. While it is strong against certain rare decks, it is not such a huge threat that one would consider facing it when deckbuilding. How often have you changed your deck, weakened it even, because it was walled by gravity shield? Personally I have never done this because most decks naturally have a way of getting around it.
Killybob, make sure you have used the card before creating a nerf thread. It is difficult to create a strong deck centered around it, and those decks have many weaknesses.
