Why are USB devices drawing power, but not being recognized by the OS?
Well - if the port works, and you can plug in multiple other devices into the port it sure looks like the problem lies in the composite device and not the mac.

The only way to know if that type of device is broken or is just not compatible (and the mac is shutting it off immediately on detection to protect itself) is to take that device to another mac of the similar hardware and test.

Experience would say just that device is broken - but you'll have to test to know for sure.