The Panzer IV was weighed to be a more cost effective anti-tank. In contrast, the T34 was weighed to be a more cost effective anti-infantry unit.
Fair game, but then again Soviets already have a lot of AI, so ignoring T3 for a quick SU-85 is mandatory with the current unit pool. That is the main issue. Half-Track, T-34, T-70 are all useless, pretty much. I am not saying that those units are bad, but you can get their job done just as good with any other T1/T2 unit combination. Considering PzIV hits @ 10min, going T3 is a death sentence, unless you desire to be on the defensive and spam Paks for the next 10 minutes.
Ideally, since Soviet progression isn't tiered, going T3 or T4 should be a real decision. The only reason I see going T3 first is if Ostheer is spamming inf like mad, but then again, some instagib mortars will do an even better job and let us not forget that the SU-85 is also very capable to give Infantry a run for their money. And Katyushkas are T4 aswell, so...
To solve, I would try this:
HT from T3 to T2
Zis-26 from T2 to T3