1) We know monks originate from Ala Mhigo, the Fists of Rhalgr.

2) We know there is more than one school of monk thanks to the 50-60 questline.

3) Occam's Razor, the simplest answer with the least assumptions being most often the right one, would suggest it is a monk who follows a different school of combat.

Whether this could be titled dancer or not...who knows? But if Dancer isn't a job expansion of Monk but instead a new job, my problem then becomes the classes are very similar, almost to the point both lose their identity.