Stock OKW t4 is GARBAGE compared to USF lategame. I don't know where you get these fanatical dillusions that the HE sherman is somehow worse than a P4 that relies entirely on RNG to make its cost worth, and a KT that is so laughably bad its seen as liability to buy rather then an actual worthwhile investment. The Jackson can handle any piece of stock armor OKW can field with enough support and the scott is a solid piece of indirect.
Meanwhile OKWs lategame AI includes, the KT which has IS2 scatter on a chasis that is 50% slower. The P4 whose AI is out matched by the HE sherman in AoE of the main gun and T34 in MGs. The p4 has to even purchase an MG to get the same DPS as the T34s MGs all for the bonus of shooting to the sides and rear. And lastly there is Obers, which arrive far later than standard mainline infantry who can simply match their power just by double equipping machine guns, all while having 5 men.
Try OKW before you try to balance them.
Did I really say OKW T4 is better than USF? Oh no, I just say USF superior late game is a myth and by your own description you are acknowledging it. Pz4 and Sherman, Jackson and Panther or Jpz4, one faction rely on a unique tool to counter armor while the other has a variety of choices and a complete army covering all aspects of the game by the moment the T3 is built.
You can't simply compare Riflemen late game in a vacuum with Obers when the first is lacking half of his support by design or to delay is own late game. When Obers hit the field, you have HMGs, Raketen, Luchs + Puma or HT + Leigs + map vision already giving you various advantages.
I repeat myself but nobody says OKW is OP or anything else, nop, but have too much advantages early game, nobody is asking for a direct nerf but an adjustement that would only bring more balance for those 5 first minutes.
Relic Entertainment
