The top request, from several commenters, but also the Editor-in-Chief of WoW Insider, was to lose the monks. He, and several readers, commented that they were skewing the list thanks to their newness, and while the original list was interesting to me, thanks to how it highlighted the dominance of pandaren and human monks, I rather agree. So, first up, the top ten most underplayed class-race combinations, excluding monks, but including pandaren. I've also added male and female character stats, thanks to the requests of commenters.
The run-down is after the break, but first, a few other observations that might pique your interest. Please do note, as before, that this is based on RealmPop's data, which, while good, is never going to be perfect! One thing I noticed on comparing the EU data and US data is the differing overall class numbers. Hunters are the most numerous on both sides of the Atlantic, followed by paladins, then druids. On the NA side, the rest went, in descending order, DK, warrior, mage, priest, rogue, warlock, shaman, monk; while on the EU side we have warrior, mage, DK, priest, rogue, shaman, warlock, monk. Now, the difference is not huge between these classes, so small variations could move the positions around, but both data sets noted a large drop-off for warlock and shaman, while the other classes hovered around similar numbers.