an at gun can tank more shots, and the su does not have the maneuvering ability to escape.
also what are you supposed to suport the su with? mines? At guns? dont answer with doctrinal units. and panthers can soak ATnades with little effort.
What I meant to say about the SU-85s advantage over a Pak/Zis was that it´s an armored unit in general. While tanks need less shots to finish off a SU-85 than an AT-gun, the SU-85 has the advantage of being armored: How many AT-guns did I lose to small arms fire? - I can´t count it. How many SU-85s did I lose to small arms fire? - One, and that was a vet 2 MG42 firing at an almost dead vehicle with special ammo from the side.
Efficient support for SU-85: One conscript-squad with the AT-nade upgrade. This will definately stop P4s and force Panthers into a 50/50 (???) situation to get their engine damaged most German players won´t risk. If you are facing Panthers you are close to a second SU-85. Alternatively an AT-gun can do.
I think Blitzkrieg should totally be reworked. That´s the problem. As of now I have no idea however how it could be fixed.