the struggle is real.
go t4 and ure Vehicle based AI is weak.
and go t3 and ure tank killing capabilities are useless more or less
Indeed. It's pretty much what happens every time when you try to use T3/4 units for your end-game.
I've been rolling a lot with commanders like Conscript Support Tactics, Soviet Combined Arms Army and the likes. Trying to use conscripts supported by T2 units and then teching to either mostly T3 or sometimes T4. Each game pretty much plays out in the same way.
I've had quite a few matches that went like this:
OKW makes lots of volks and some supporting units, gets Special Operations Doctrine for 10 ammo super grenades. Rushes out Obers to hardcounter all my infantry and using all the ammo he saved from having basically free grenades to get schreks on all his volks. He moves around in big pushes that trample everything in the way including tanks. Then at the end of the day he gets either panthers or KTs and it's game over. I can't make big investments in AT because the man-power bleed caused by obers and 10 ammo grenade barrages is enormous, and my medium tanks pose little of a threat to a group of schrekked up volks; you can get 1-2 shots in before you have to pull back for repairs or lose your tank.
It seems for me that the only way to beat OKW is to go for call-in commanders and skipping T3/4 all together. You will get better tanks that won't instantly lose all their health to panzerschreks and you can spend the manpower you save to get another squad or an AT gun to deal with panthers.