The German campaign seems to be a lot harder because their vehicles are useless and cost too much manpower/fuel for no reason.
Soviet get T34/76 for 300 manpower and 80 fuel. Yet the Panzer F1 which can barely damage T34/76 cost 450 manpower and 125 fuel. KV-1 is fine though costing 600 man power. AI barely builds them unless they get it for free.
Stug 3 E needs to miss less against infantry. It cost 320 manpower which is a bit more than T34/76. Yet Stug 3 can't do any damage to T34/76. In Operation Barbarossa the vehicles are mostly not worth building because they cost too much to build or can't penetrate.
Since these are Theater of war vehicles.