My dude, they have bits and pieces to pull from wherever they want. Russel the Bard, the Bard April Fools joke, random Bards. You're dramatically overselling the forethought put into Pandaren lore in Warcraft 3.
You really shouldn't argue so hard with *me*, considering my initial post was in *defense* of new class ideas. It wasn't directed at you, just because you want a specific two class(es) and don't like when other people have other ideas. I'm one of the people who is completely for new class ideas. In all senses.
Lore explanations are easy. All of these points aside, give it up. You have to stop taking the lore and "things being set up" so seriously, anyway, because obviously the writers don't.