I think one of the main problems graviton guard suffers from is that he's expensive because he's hard to kill, yet very rarely will an opponent want to use CC on a creature that only does 3 damage with no special abilities.
I have not encountered any successful decks using this card. It might occasionally come up in rainbows, but even then it's because the deck needs to balance quanta, not because it's a particularly useful card.
I think the best solution just a simple cost reduction. Not everything needs to be fancy, and if we give ALL of the mid-hitters abilities then we're nerfing luciferase, which really doesn't need nerfed.