The Forsaken never should’ve joined the Horde.
I would’ve been happier if BC had brought a third faction, made up of Blood Elves, Forsaken, Naga, and Broken Draenei as the Illidari. The Forsaken would’ve fit into that group much better. Varimathras wouldn’t have stuck out like a sore thumb. Illidan would’ve probably lauded the Forsaken Blight rather than condemned it.