I also have a Cat C-7 powered DP. Always runs between 186 to 195. Even up steep grades in high heat, its never run over 200 pulling a toad. Check that radiator and make sure the slobber tube is extended to the rear of the coach behind and below the radiator.
In 28K miles, haven't had any issue with the motor except an oil leak near the turbo line. Its been a great engine so far. I do run Optilube XPD diesel fuel additive to counter the lubricity lost due to ULSD. IT seems to work great. No injector issues.