Ah yes, Cobalion the Mienshao counter. Sounds like a plan.
Anyway, Mienshao is really good. Fake Out... is not. Ambipom is not entirely outclassed by Mienshao, but I guarantee you there isn't a single team where Ambipom is used that couldn't be improved by replacing Ambipom with something--not necessarily Mienshao. It's just not a good Pokemon.
That is all.