Well we cleared out the black temple and arrested illidan some expansions ago. And sacked the legion home world/imprisoned a god. Hell, even thrall took his family to nagrand which is to this day infested with evil orcs, and hellfire citadel is still housing kargath(lul) and his cabal.
Theres a plot hole here that needs some make up.
Or just add red skin and crazy tusks to our orcs and be done with it