This is a tough one. If Germany gets pulled in with the Allies against Russia, it could work for them but I think it may have more likely worked against Germany's favour. While the British/French would inflict casualties against the Russians, I doubt it would have been on the scale the Germans did in reality. Such a conflict would have probably ended in a stalemate - with Russia winning the land war but not being able to strike back at England or France. The battle would move to the Middle East and Asia - Russia vs the English colonies. Despite the casualties, it probably would have served to better prepare England, France and Russia against any future German moves.
Arent you missing one little country or two in this equation? Lets start with the US maybe. No lendlease to Russia. Also we did have a bit of an Army , Navy , Airforce and Marines. Another country you seemed to dissmiss is Germany Herself. I really doubt Russia would have stood long against Britain, France Germany, Austrailia, Austria, Canada and the US just to name a few. Ill tell you this if not for Japan we may well have gone the otherway. Its hard to imagine a scenario where the US and Japan are on the same side back then. I also see no real reason to back Stalin over Hitler. If we were really serious about ending war we should have finished the job. Yes it would have cost millions of lifes but it would have saved and freed millions more.