Yeah, that was exactly what I was thinking. They can still be active without the Lich King being active.

But Bolvar is supposed to be a secret so if we work for him, than it would probably be from very "high ranked" NPCs and nothing too obvious.
I really like the idea of Bolvar helping us though. like the Clone army in Star Wars. Than in WoW 2 or Wc4 Ner'zhul would become dominant and they would turn against us.