Recall is it's main counter since it removes all buffs, but yeah, there's not many cards for recalling an enemy, I think only Ionia has recalling right now. So the only other option is to out-aggro/kill your opponent before they get too big, since the one negative effect on them at the moment is they can't block.
Because they have very little counter-play, are so cheap for their value ( only a 3 cost for a 2/2 version ), and can be combo killed for MASSIVE value as mentioned, I definitely agree they're pretty OP atm. At least making it a 4 cost 1/2, would be slightly more balanced.
But until they get re-worked, I definitely know what at least one of my classes and cards I'll be shooting to use for expeditions and ranked hahaha