"Loyal to the end" simply does not work in WoW. In a tabletop RPG the GM will give you fitting consequences if you play fully evil. Your character is not gonna be heralded as "Champion" for long. You are in a world with rules. If your character breaks them and pisses the wrong people off you will loose your head for it.
I can imagine the millions of threads exploding when Blizzard actually "kills" the Loyalists in SLs, because they were hellbent on being "loyal to the end".
It's really that simple: The villain Sylvanas will not win. Because if she wins the universe ends. So everyone that associates with her will loose too. If the Loyalists are aware of this and want their character to go out in a blaze of glory that is fine with me.
BUT we all know they are not. They will go and be evil because it is keeeewwwll, and then they will cry our ears off when the game actually imposes consequences on them. No matter how many warnings Blizzard put up, the shit storm will be epic.
Blizzard, being fully aware of this, is avoiding it. Obviously.