I agree with the stats being too high.
The cost, by extension, is too high.
Shockwave is air, and it does 4 damage and destroys frozen creatures outright, not gravity, and not that effect. It should have a name change.
Even then, I would say I'm not a huge fan of the idea. Otyughs can eat creatures, including some bigger than 5 if they grow a little, have less cost to do so, and benefit from it. I'm also not a huge fan of trying to balance by allowing only one at a time in play. The cost should take care of that, itself, and so long as the card isn't excessive, it shouldn't be a problem having more than one, but that is just personal preference.