I <3 how bad the lore is in this game. There are defenders, there are Dragons, there are Night Elves (whom, as canon, have spent the past 10000 years preparing for another Legion invasion), there are Ancients (Cenarius), but the writers forget about this and put contradictory canon in.
but w/e...
Um, no. If they want to go ahead and retcon out the Long Vigil they can go ahead and do it to validate the Black Morass line. It wouldn't surprise me one bit given the state of lore. Until then, both are equally valid, and Im not going to waste time arguing *that* point so we can agree to disagree early on.