I'm an advocate of X2 T-34/76 or an AT gun and one T-34/76 are better than one Su-85. The real advantage of the Su-85 is its range, but requires a spotter to take advantage of that. Its frontal armour is weak, and fuel wise, it is expensive relative to a T-34/76 but dies just as easily and has all the disadvantages of a casemate mounted AT gun. Two shots on target from a T-34 is better than an Su-85 getting in one or none as it traverses its gun if your opponent's micro is superior. Use the T-34/76's advantages of speed and turret to flank and fire. Ram with one if needs be and kill with the other, situational of course.
T34/76s suck and are only half decent as ramming tools and inf crushing, the Su85 can deal constant damage with high range and RoF, and as it vets up it will become a mini Elefant and be able to kill a panther alone. The thing why people only use the T34/76 to fight Lights and other mediums (Not a panther) is that their penetration is absolute shait just as their armor. Mobility on the other hand is ok, anti inf is ok but against "real" tanks the T34/76 is absolute shit