Its going to take at least another expansion to give Monks the depth and iteration that the other classes have from word go. I can't really comment on Monks other then that as I haven't played one significantly.
A lot of the representation statistics could still be to do with the fact that people on the whole went into MoP as their main character, and didn't do many alting. It will take a long while for Monks to be as widely played as the other classes in my opinion.