An army here and an army there and pretty soon you've lost a whole lotta troops. The best General Staff in the world and Hitler overrules them to make bonehead decisions over and over.
I think if the Russians had cut an armistice with the Germans it would only be for the purpose of buying time to gain strength to get back whatever they had to give them.
Knowing Stalin, I agree. The key for the Germans would have been for Stalin to have been deposed in one manner or another.