This is purely from a historical perspective:
The T-34/76 tank was the best tank of WW2, and according to some lists, even the best tank of all times. This tank made a great impression even on Heinz Guderian. Therefore I do not understand why this historical fact is not reflected in the game. I don't expect to see so much of this tank in the game, if it is placed in T4 and has a population cap of 10.
The T-34/76 was the best tank in the world, in 1941. It's armour could deflect nearly everything the Germans had en masse. Pak 36, Pak 38, Panzer III 36mm Guns, Panzer III 50mm Guns, Panzer IV 75mm Infantry Support Guns. Only the Pak 40 and Flak 88 could penetrate it at decent range. It could also penetrate the Panzer III and Panzer IV Tanks.
In 1942 the Germans altered the Panzer IV significantly, doubling its armour and giving it a Pak 40 based gun. The T-34/76 had lost it's advantages against them. And obviously the Tiger I had no trouble with the T-34/76.
The T-34/85 didn't improve the armour situation as far as I know, it just allowed the T-34 to engage on equal footing with the Panzer IV, and Tiger I if it was close enough.