oldsouth,
Though it may not be comforting to run the engine consistently where the coolant temps exceed 100 degrees C, it is not a problem for a properly tuned vehicle. The red zone is at 120C for a reason.
That said, given the history of head problems with the OM603.97 engine, I would be just as interested as you in keeping coolant temps under control. The fact that the problem worsened following a supposed fix by the dealer necessitates a return trip.