You gotta find a way to add that orc and his drums to some other animal, because it is too cool of a unit to not appear in anything pre-Kalimdor just because his mount is from Kalimdor.
I was thinking about bears, since forest trolls already ride bears in WoW (now everyone does), their sizes match, and bears can be found anywhere. Or to catapults in some way, though that's harder. This way they may be used for your Second War project too. As well as being a damn cool model.