They're not orcs or humans, and once the expansion is over it will no longer be the expansion in which they were introduced. Therefore, they will get a few random lore nuggets here and there that don't amount to much and no real explanations for anything. *shrug* That's just how it goes.
I can't think of any particularly good lore reason for the pandaren of the wandering isle to continue to fight one another. The faction split didn't go well for them, and the two primarily responsible have reconciled.