Heer had an excellent tradition of troop replenishment (training reinforcements before throwing them into battle). However, as the war progressed, Heer started to founder under the mounting pressure of numeric and material superiority of the Red Army (also, the losses among battle veterans mounted and the troops became weaker).
Hitler, faced with a cognitive dissonance (his Ubermenschen are being defeated by Untermenschen), chose to blame the Heer (from privates to Generals) and decided to form Waffen SS (which were similar to Guard troops in other countries).
Heer resented this because it starved it of men and materiel and reduced its prestige. Thus the German Generals tend to claim in their memoirs that Waffen SS were poorly trained (probably true), better equipped (probably true), less battle-effective (hard to verify), and more prone to war crimes (not necessarily true - not because Waffen SS was innocent, but because Heer was just as guilty).
Incidentally, this was not the only case of German land forces fragmentation, the other being Luftwaffe Field Divisions.
No matter what Germany would have done after 1942 could have changed the final outcome. They could have been more efficient, but the end result would have been the same.