Uh, the entire point of the T34/85 in it's stat distribution and were it's placed on the call in/time system is that it's supposed to be the Soviet version but tweaked a little. It does well versus tanks, and well against infantry, that means it's kinda superior to the Panther in AI but less so in pure AT power.
The PIV in a world with out the Jackson is just like the T34, a medium tank that kind falls off late game when the heavies come out, but since the Jackson is a thing that exists the PIV and by combination t3 just doesn't fly.
Putting it in t3 would just make the little medium armor Axis does have even more irrelevant, unless you changed the tier system and unit lists for every faction.
First off, let me quote my first response to you which got drowned off.
I also don't understand the people who say that a doctrinal T-34/85 should be better. No it should not be. Doctrinal units are there to provide additional options. 85 pigeon holes players into picking it by being a straight upgrade to a stock unit that is worthless. There's no excuse for that when it would still be balanced as a stock unit. Even more so since you would have to pay for your teching.
You guys can't complain about a call-in meta and then insist that doctrinal units should be stronger hands down. You can't have your cake and eat it. Either you solve a lot of problems by making 85 a stock unit when there is no reason it shouldn't be, or you can continue whining both about the call in meta and a hypothetical 85 that will somehow suddenly be imbalanced because its unlock parameter changed from pick one of the few viable doctrines and wait until 10 CP to pay 120 fuel to unlock it and use it with any other doctrine the faction has access to.
With that out of the way, no, the tank that you're putting on a pedestal is not that much better than a Panzer IV which still has many advantages with far better veterancy and Panzer Tactician access, and MG, and Axis has heavier tanks than IS-2 in the form of King Tiger and Jagdtiger. Panther is also a very effective non-doctrinal AT.
Panzer IV never ceases to be useful; it can hold its own well against IS-2. Just not alone and not very cost effectively, but it's by far not to be considered useless. It's not less useful than T-34/85 either, which it itself is not bad.
And edit to respond to your edit: T-34/85 would be perfectly balanced at T3 and would not need to be nerfed. At all. It's a slightly better Panzer IV that's still worse in many ways.