Q u o t e: The Baron's mount is a very rare drop, and is usuable by any class and race in the game. The drop rate is based upon the unique loot table of the Baron and not any special circumstance or requirement. Also this predetermined rate is identical across all realms, in all regions of the world.
I did hear a rumor that if you party with both a Shaman and Paladin (don't ask me how that's possible) the drop rate will double, but even then only if they /hug during the exact moment the Baron falls dead.
After having investigated the rumor on internal realms I've discovered that the drop rate improvement only occurs if both the Shaman and Paladin are Gnome characters. Also, both players must be wearing t-shirts that depict a baby Pomeranian equipped with one of those plastic funnels designed to prevent self biting.
I tell you, our devs create some really wacky easter egg formulas.