Nothing is more of a tease than dangling an upcoming raid boss in front of players a week early. MMO players thrive when there's nothing to do but wait for the next patch, so if a boss is just sitting there, they're going to look for a way to kill it against Blizzard's wishes.
And they almost would've if it wasn't for Blizzard ruining the fun by implementing a safeguard to prevent anyone from actually pulling it off.
