@Erik:
Alright, tried Smolensk a few turns (7) and my first impressions:
1. Cut down enemy reinforcements (=credits to 0). The russians are way ahead of me and I have no chance. (I can play this game, I am not stupid. But this is not balanced.)
2. Give me more air supply. I cant even deploy everything I have and I have more than 3500 (I kid you not) credits in the bank.
3. Neatly ties into 2 - the Russian airforce is waaaayyy too strong.
4. Increase supply in the base area. Massively. Right now, one (2 strength) Russian tank can move on a rail supply link and cut my whole army off. Absurd. Be a bit more lenient here.
5. Generally, this isnt Panzercorps. You cannot port 1:1. This is never-ever going to be fun or playable if you keep this up.
After playing some of the missions you did for this campaign (great work, still. Could not do it myself

), I think the general feedback I can give you is:
1. No resupply to the Russians until at least Moscow.
2. Combat is less harsh in OoB. So cut down Russian units (and everywhere else) and set resupply to 0 or after Moscow maybe to 2 per turn. Seriously, this does not work out in any other way.
3. More supply for me. Maybe even more command points. If you feel like this should be a massive army I am commanding, go for it. (This strains hardware. I would still suggest keeping things smaller.)
4. More roads, more turns. Even if Russia had no paved roads in 1941, who cares? This is about fun, not accuracy.
In general, you cannot move this 1:1 from Panzercorps to OoB and expect a playable result.
OoB gives you a lot more possibilities in terms of supply, credits options and so on. Use them. And with the OoB AI, the Russians are way too strong. They should be reeling until Moscow, at least.
So, most important: Make me stronger, make them weaker. This is not about incompetence, but after a few turns I can already tell this is not going anywhere.
BTW, why not add commanders in this campaign? Can you actually edit them? (Sorry, dont know anything) If yes, they could be the great equalizer.
Keep up the great work, Erik.