The problem with Wehrmacht is that some units really over perform such as LMG Grens, Paks, P4's, Tigers. Whilst as a lot of under perform, basically everything other than those and other things such as Mortars Stug E etc. There really is no reason why Wehrmacht should not just spam LMG Grens into Paks, P4's and then Tiger to close game. Wehrmacht really need to get their units balanced out so there's actual variety and unit mixing, it's supposed to be a faction of combined arms, but it's so far from it.
I wouldn't say that these units overperform (except lmg-grens), it's rather that they're the only units actually viable. Maybe I'm entirely wrong but in my experience gren spam won't get you anywhere. Depending on map and opponent there's almost always a need for an mg or mortar or even a sniper, so at least for me combined arms with Ostheer is the only way you can actually expect to win.