All the legendary weapons (minus BC) were exclusive. One person would be chosen from their guild and they would get the item. Shadowmourne and Tarecgosa (and Atiesh and Fangs if you want to count them) had bonuses other than being stat sticks.
Blizzard has released a legendary that everyone has a chance of getting and people are surprised that who ever actually got it get's a little something extra? I'm wondering if the people who are complaining were subbed before LFR was a thing. People should be grateful that Blizzard made this legendary so accessible and complaining about something as small as a world boss for a legendary that again, everyone can have is pathetic.