Unless you can push your enemy all the way back to his base and destroy it, the german player will simply keep reversing while taking pot shots at the su-85. The shocks will eventually run out of steam leaving those at guns all alone and ready to be picked off by any infantry.
3 AT guns, su 85, and shocks for support
A t34 would have been better since it could atleast try to flank them, but then the AT guns aren't really the ones pulling the weight.