Technically, Sir Zeliek (one of the four horsemen in naxx) is/was a paladin and still uses the light in much the same way. I'm not saying udnead should be able to be pallies, but it would make mroe sense than tauren or pandaren.
Dwarves were among the first paladins, possibly because of their close ties to humans, but they definitely were paladins pretty much from the start.