One way to see if the water is hot in the water heater, but is possibly mixing with cold water via the crossover valve....is to go outside and briefly flip up the lever on the pressure/temp relief valve located on the face of the water heater. Make sure you are not standing where you can get splashed with hot water.
It the water is real hot here, then you know the problem is not at the heater, but by the time it gets to the fixture (a crossover valve being open (when it should be closed) letting cold water into the hot water line