Yes, I mean exactly the changes that made P4 completely murder infantry while not really changing anything against tanks it beats and was beaten by, the changes that made Ostwind valid AND cheaper alternative to P4 while making it a little bit more affordable AA and the changes to StuG that made it murder infantry and let it be spammable general support for either Ostwind or P4.
The change that made it murder infantry is actually an unlisted change, since it's unlisted I don't know where it was. The change was the hull machine-gun was changed from 2 to 4 damage, doubling its DPS. Before that, it was similar to the T-34's hull machine gun, which we know is very weak.
The synergies are still there and while P4 is clearly the top of the current T3 food chain, StuG-G is still a viable choice, just not as the first T3 unit, HP nerf is meaningless against anything other then SU-76, PTRS and zooka and it lost quite a number from its cost.
They aren't there. The StuG is side AI/AT, the Panzer IV is side AI/AT as well but better at both. The StuG no longer dedicates itself to any role, the only difference is the Panzer IV is more durable and has a turret and better scaling. The only reason to get a StuG is if you're desperate or you plan to get at least 2 and use spotting scopes and Panzergrenadiers.
Take a look at the cost changes-the underused units were made noticably cheaper while not really changing their performance on the long run while P4 became best stock T3 armor in game, being deadly against both, armor and infantry and being durable as well.
The problem with that is it's better than stock tanks, but weaker than call-ins. Which means nobody uses the stock tanks because they lose to the Panzer IV, but nobody uses the Panzer IV because they lose to call-in tanks. In the end it's all Call-Ins and Panthers. I don't think the Panzer IV needed that armour buff, I wouldn't actually mind it or the MG buff undone, or both if the cost increase is also undone.
The meta problems regarding Call-Ins, the M36, and OKW also need to be addressed for a healthy Wehr T3 (and allied factions) to thrive again. The "bigger is better" meta is bad for gameplay and I'm quite sick of it, I just want to use my beloved medium tanks again without hindering my chances at victory. (Note: I'm talking about 2v2 and up)