@the whole "April Fools joke" people:
Afaik Metzen had both illustrated and had given the Pandaren a page in the published original Monsters manual for the table top edition of Warcraft BEFORE all the crap you people refer to and possibly even the inception of the video game series. (I can't remember the dates even though I remember playing WC1 fondly as a 15 yo after school and work.)
I'm 99% sure there is proof of it. Iirc Bash linked it a little while after Blizzcon to shut people up. Strangely I've NEVER seen a single whiner include that point when arguing against it.
I'm way to lazy to look it up but the drawing is of a Pandaren, a (one of those damn bear things from felwood) a gnome and some other creature in it. Yeah I realize the memory is a little shaky but in general its correct even if the details are a tad fuzzy.
Look dude preliminary sketches and concept artwork don't mean anything, we have Tauren space marine concept art as well. If blizz came out with the world of warcraft: Infinitiy and beyond expac, we would call it a toy story rip off. The fact blizzard had space marine concept art before toy story wouldn't matter its the audiences association with the material and the lack of separation of that material (artistically and thematically the two materials are very close together heck (kungdu panda, mists of pandaria).
At some point a conscious decision was made internally that Panda's do not fit into the warcraft mythos and were more of a gag of WC3, thus the material was used in an April fools joke. Now a few years later running low on creativity that April fools joke is being implemented. Its evidence of a creativity vacuum, "we can't come up with anything new or interesting, lets just flesh out an old April fools gag into an expansion".
Would you be satisfied with a fully playable hero unit in WC3?
All you do when you insist they were never 'really' part of the lore is show how little you know the lore.