I'm not so sure about that F.S.
If you take a look at the amount of territory covered, equipment destroyed and number of prisoners taken, I'd say their chances were pretty good.
True logistics were stacked against them, but up until late 1942 they had a pretty good track record for pulling off the impossible.
Plus, they had wireless communication.
In my opinion, what put the nail in the Ost Front campaign coffin was the nazi policy that came in behind the Wehrmacht. When you see photos of hundreds of Russian prisoners being herded into captivity by a hand full of Heer on bicycles, that's not a "difficult opponent", that's an army that would have turned on Stalin for food and decent treatment.
Hitler screwed up plenty as far as the war went but it was nazi brutality that turned a people who, in large numbers, at first saw themselves as liberated rather than conquered and turned them into hardened enemies.
Had the Russian people been treated well, there are many who believe they would have joined the Wehrmacht by the millions and eventually Stalin and the Soviet state would had their backs to the Bearing Sea.