yes, I think you are correct.
the most probable (and definite!) cause for a dead CPU is using the wrong power cable. I don't think there is a second way to fry a CPU in general use. As the CPU is not consuming a lot of power in normal operation, a heat-related failure is also very unlikely.
The main problems of the DDX are still heat in the power supply (therefore failing caps, regulators and diodes in the power supply), failing caps in general (especially on the LCD board) and a swapped power connector on the CPU card after cap exchange
I have checked with a thermal camera, but there are no heat issues with CPU or DSPs. Apart from the power supply the ADCs are running hot, too, but I have never seen a failed ADC so far.