I have a 21 yr old Delta Bath Tub 1500 or 1700 model Water Control Valve.
Mine is the kind with a separate volume control from the tempature control dial.
When you select the maximum hot hater, the tempeture is not that hot, less than the sink hot water temp. I tried to adjust the limit ring ( maximum counterclockwise setting ) and that did not raise the tempeture much compared to the sink hot facet. I am told by Delta to replace the cartridge. Does this sound like the solution? There is no water drip afetr shut off, just a lack of hot water mixing.

If delta suggested replacing the cartridge, I would certainly start there. Most likely it will be the solution.