Because Alleria of the Void elves can single-handedly solo Quel'Thalas.
> Teleport into Sunwell Plateau (her teleportation abilities seemingly have no limits)
> Go near the Sunwell
> Touch the Sunwell
> Literally GG
I expect Horde players here to agree fully with me. After all, aren't the Void elves a "threat" because they can easily endanger Thalassian civilization?