I was going to use Muk-A primarily because I'm having a hard time finding a reliable Blace counter. Clefable needs a lot of SpD to avoid the 2HKO from specs blace, and the 2HKO from ghostium z and flamethrower, to the point that it can't reliably check Hawlucha, Mega Loppuny, and Mega Heracross. Chansey can't do anything to Blace, and Pyukumuku is in the same boat as Clefable (and it also relies on spite because of sub, and you can't trap Blace).
Do you have any better suggestions? I was thinking of Hydreigon, since it doubles as a Heatran check, but it is hard to fit on stall (Heatran is usually checked by Mew or Moltres, which check Lele and Kartana respectively).