I played CORE on HOI1 and was happy to see the evil Bolsheviks put up one helluva fight. But then I tried HOI2 when it came out and quit soon after out of boredom cause it was as easy as taking vegetables from a dog. There's not much to read about this CORE's difficulty but it seems the Soviets are still very weak. If you want to make it balanced for people not playing as Germany, why not boost the Soviets a bit more to avoid a lame cakewalk and then make a 2nd version of CORE which is for a German player (or for an Axis player).
In the German player version of CORE, you could make it like HOI1 CORE so that the Soviets are actually strong and put up a good fight requiring players to replay the game a few times before defeating it. I'd even prefer it so that the Soviets are nearly undefeatable as the Axis unless a very careful strategy is employed against their hordes... of course without using gay exploits like building level 10 forts all along the border or anything like that.
It's so hard to find a challenging PC game.

Please consider my suggestion about an Axis player CORE.