I'm rather inexperienced with the card game itself, but I really do not see a point to the attack Gravity Slam. It deals little damage, with its maximum damage requiring an enemy to have no power stat at all, and has a cost of 2, which could easily be spent on other attacks that more consecutively deal as much if not more damage on average. Even Pebblestorm seems more useful, and it requires the user have the right elements.
Speaking of Pebblestorm, I feel that its build cost is unreasonable when you consider the only way for it to get full damage is if the user is proficient at air and earth attacks. Sure, many Mipedians would benefit, but we often see the move (in the show) being used by Overworlders most. Even if it does have the ability to do 10 damage, its cost of a build point makes an inexperienced player such as myself to think it would be more useful to spend that build point somewhere else.
Again, I am still not very good at Chaotic, so what I've said above may well be completely wrong.