Yes, Germans never lose ! Actually they should have use better protection if they thought that there will be a counterattack - in other words - they sucked ! It was German idea to keep Romanians here and they payed the price when the badly armed allies were overrun.
If they thought there would be a counter-attack, then the flank protection would be better. But the Germans belived the Russians to have exhausted themselves over the last two years, something which seemed rather realistic at the time if you ask me. And since then a Sovjet counter-attack would seem unlikly it would make sense to keep the low-quality troops at a place where fighting in any greater degree wasn't likly to happen and from where high-quality troops could then be taken from simple guard duties and put where they were needed.

Once the offensive came the Germans and their allies were simply to supprised to be able to respond quickly enough and powerful enough. Hitler's well known confidence in that fixed defences could withstand anything also made what it could to make the disaster greater.

In my opinion the Germans didn't really do anything wrong, it was the Sovjets who did things right.