Are heavy damage and light damage mutually exclusive?

This answer on the KoA boards might help ya: http://forums.reckoning.amalur.com/showthread.php?6582-what-are-lightly-wounded-targets-Gem-question-I-think. Summarizing: it does sound like they are mutually exclusive states. What's not clear is where the dividing line(s) are for lightly wounded and heavily wounded...seems like lightly wounded is about 75% health or so.