Considering the only ball/bomb move Slowbro gets is Sludge Bomb, I'd say it's much better off the way it is now.
Overpowered? It just clears effects, it's not that OP.
but is realy very overused, they could let other moves have role or make addictions to other moves...
like Inferno... could destroy terrains maybe instead?
we have Brick Break and Psychic Fang to remove screens,
... now addition in steel roller to remove terrains...