Brute force you said? Allies Vet3=>better then OKW vet 5 if all you infantry (mostly just volk if you even get there) and let not talk about the weakness in Tank and Indirect fire of the OWK.Just do this comparison
Vet 5 Volk vs Vet 3 Shock
Vet 5 Volk vs Vet 3 Rifle fully armed
Vet 5 Volk vs Vet 3 Section with Bren and sniping LMG + Lee–Enfield.
Vet 5 Volk only win vs Vet 3 Penal and yet it is still a long shot sometime.
the rest like Paratrooper,Ranger,......Concript?Concript can't win right?Right?
Easier way to fix give OKW a doctrial that allow for a TigerI call in for the late game, need some sort of heavy tank that can stand their ground and support infantry.
OKW got 6-7 types of infantry. None of them is builder only or narrow specialist, all of them perform well in combat in different, but not specialist limited situations.
What makes you believe OKW was meant to be carried on the backs of volks alone?
Volks are axis cons, they will carry you through the early and early mid game, but they are not going to compete against much more expensive squads with much more expensive weapon upgrades, so use your own elite infantry.