How did you come to that conclusion?
The devs always stated that the t34/76 was mainly an AI unit and not meant to be good counter to tanks yet they decided to buff it's AT ability. I personally never heard them say that about the t34/85. And even if they did their design concept could prove to be wrong in game play.
Looking at the commander as you suggest, I see almost half its abilities dedicated to AI including heavy mortar and guards (except for button they dont do much damage to tanks). Field repair helps tanks but hardly when rounds keep bouncing. Mark vehicle also helps allot again if rounds penetrate and that's the problem with this tank it just doesn't penetrate.
See where the problem is?
PS. often times in 1v1 you have to skip t4/su85 to get the t34/85
1) I came to this conclusion for various reasons the primary ones being the RAM and the fact that mark target gives 50% extra damage , that means that its supposed to be used by uits with relatively small damage and relatively good penetration like atgs su76s , guards and even at grenades ( the 2 latter used from behind ) . Other than that there were many more cooler ways to give a hard at unit on this commander other than the 34/85s (like is2 for example or kv1 ) but they didnt want any because the commander is supposed to buff many aspects of your army but not by much
2) I think you are using the commander in the wrong way . 1st of all guards are soft antiinfantry , hard antilightvehicle and soft antitank (though with good micro they get a lot better against tanks and infantry ) and the 120mm hits light vehicles like a ton of bricks . Regardless of that you are supposed to have early game dominance using this commander , that is what i told you in the first place , that is why you have the 120mm and the guards and since you dont have big munitions abilities you are supposed to spam mines and flares like a madman in order for your cons guards mortar atg etc to kille even more germans . Under those premises you should have a large combined arms force kicking ass long before you call in the t34/85s , you aslo should have a fuel and manpower advantage over your opponent which will allow you to call the 34/85s and creaTe a really big combined arms force that can deal with anything , you cant be on the back foot all game relying on just t1 or just t2 and expect to turn around the situation with that ability .
All that said , i do think the 34/85s need a small buff and definitely same fire rate as t34s , i said so before .
But if you want them to beat p4s head on , then you need to have the ram removed and they cant be a call in , they should be recruited like normal units and the mark target and crew repair need to take a hit with the nerfbat as well . Or go the way nullist proposes with a munitions cost upgrade , allthough imo you should also need to upgrade it from the t3 building in order to use