Towards the end when everything was disintegrating I think it was more than wounded soldiers getting discharged who simply left.
That being said, this does bring up an excellent point. Tactically, the Soviets usually suffered casualties along the lines of between 5 and 10 to 1 when fighting German formations. The Soviets on the operational level after the first year were usually suffering losses more along the lines of 1-1 though. From Stalingrad on, the Germans were making very serious errors that played right into the hands of Deep Battle, making most of their forces irrelevant. From placing poorly equipped and motivated allies on their flanks at Stalingrad (and stripping their panzer reserves for the fight for the city and the attack into the Caucasus mountains), to attacking directly into the teeth of the best defenses the Soviet Army could put together at Kursk (leaving themselves open for a massive counterstroke), to massing most of their mobile fighting power in Rumania in June of 1944 (leaving Army group center open to destruction without many mobile reserves to counter Operation Bagration), to refusing to evacuate hundreds of thousands of men from the Courland pocket, to throwing in their last reserves into futile counterattacks around Budapest instead of reinforcing the Oder line to the East... on an operational level, with a few exceptions (ie Mansteins' counteroffensive around Kharkov in the Winter of 42-43) the Soviets were superior to their German counterparts... and that made up for the disproportionate number of casualties that they suffered at the tactical level.
If Hitler had done as Manstein had asked in 1943, and given him complete control of the Eastern Front then maybe he would have been able to fight Zhukov to a draw... then again maybe not. Instead he got relieved. And we have a reality of German tactical superiority that turned itself into a myth of German operational superiority (that in reality didn't live past 1941).