The Scout Car alone is the biggest problem OKW have, and in team games Maxim spam can equally be a serious problem. In the case of the latter, Wehr cannot defeat said Maxim spam fast enough for the OKW player to really be able to contribute anything. A horde of averagely-micro'd Maxims can punish an OKW far more than it should be able to for the amount of input it takes.
The biggest problems for OKW are, to summarize the above:
1) fact the Panzerfaust isn't unlocked once the 1st truck hits the field, but instead once the first truck is completely deployed (should be addressed)
2) fact the Indirect Fire unit (Leig) is locked behind tech, and only one of the two trucks as well (possibly could be addressed by placing it in HQ like the MG 34, maybe even still requiring tech, or maybe being T0 but with a higher upfront cost.)
Your first point with the Faust, could be dealt with Commanders who have Pfusiliers
The second point I agree 100% the Leig should be in the main HQ, otherwise you are screwed agaings any allied support weapons