I've modded the Soviets up some and the Germans down quite a bit. I've also changed some things like basic unit values, increasing all other units except for the tanks.
Here's where I think the problem lies:
Basically once the Germans invade Russia (if they do it in Summer 41) they've had quite a bit of time to build units and get experience. In my last game (which was modded but not as heavily as it is now) I managed to last unit late summer 42 before the deathstars got me. At the end, I see that some German tank armies benefit from level 4 war doctrine, 90% experience, and 20% leader experience, putting their combat values in the 30's. Not to mention, they had as many panzer units (corps & army) as I had units during the high point of the war for me.
Unless you're behind a river or in a city, you don't survive the first attack.
What I've done in a nutshell is lower German land warfare doctrine levels, max leader experience, lower the rate at which units gain xp from combat and raise the value of all types of units except for tank armies & corps. I'll run another test game tonight after I eat and post the modified files if successful (and if you guys want them).
Make wargames, not war.