What's the best way to deal with/counter the centaur AA?
Mines are your best bet. Typically Centars get used very aggressively to instant wipe units (at least until they get patched). Mines damage engine without the cost of a faust + gren squad. once its slow, its pretty much dead in the water and you have to capitalize on it.
If you still are really worried about it as Ostheer get a StuG or as OKW a jagdpanzer IV