Well maybe the soviets had betters amounts of better quality tanks than the Germans
For example there are 2 t34/85's to every Panther and that's really the best tank the germans have. Maybe giving one more panther to a map would be acceptable. However if you take that number to account, there were also 3,500 is2 tanks built. So every 3 panthers there should be about 2 is2's, and one Tiger I and/or or one rare tank. I really don't get the big deal about upping the gun and armour of the panzer4 anyways? In game you can penetrate the front plate of the is2 and both t-34 variants. And if angled you can deflect shots from all tanks. Armour thickness in RO is really an important factor.
Another thing about crappy loadouts, there are very few vechiles that come to the thousand mark but are actually superior to the panzer4. For example the hetzer and marder series all used the 75mm gun. The other tanks like the King Tiger, Jagdpanther, Nashorn, Jagdtiger were produced small quantities, in hundreds. You would get only one of a one of those rare tanks in a map. Regardless they should probabley modelled.
At the same time several russian tank destroyers haven't been modelled even though they were produced in greater numbers than all those tanks, this would keep a balance. The ISU-122 and ISU-152 combined, were made in a produciton of about 4,000 tanks. So they should supplment the heavy Russian armour, the Is2. Also missing is the SU-85 and SU-100.