Eh, Panzer IV is fine-ish I think. Jagdpanzer IV and Panther are good units in a bubble but don't really have much of an impact on the battlefield. I mean, yeah, a Panther beats a Pershing, but I think the arrival of a Pershing has a more significant impact on the dynamics of a match. The Jagdpanzer, for instance, is basically useless in any offensive context.
Also, I think Katitof is right about OKW being intended to have a smaller armour presence than other factions, although that's 2014 logic and I don't know if it holds true any longer.
The powerful units Katikof is talking about have long since been nerfed. Now that OKW needs to spend 70 fuel to even get healing (truck, truck setup, side upgrade), a 150 fuel medium tank is a bit of a high price if you ask me. The original 135-140 would be better.