the real question is: why do you think it's fair?
Steal already seems a very solid card, with very important differences regarding other kinds of PC, by allowing you to get an opponents permanent instead of just destroying it, wich might enable you to completely ruin some strategies or even "steal" (no pun intended) the other's deck strategy
even if you only manage to steal one bone counter, and that's not a steal property, thats a BW property, it can pottentialy lead to you being able to build up one wall of your own after you take down your opponent's, although that's not a very common scenario.
Overall, i think the way it is right now is just fine. besides, BW is supposed to be the "anti-PC" shield because of its numerous bone counters and ways to make it grow