No, Hakkar himself doesn't make an appearance, but his blood curse does -- quite an appearance. Despite its 3 second duration, a group of pranksters (most likely) managed to bring this debuff to Orgrimmar on Blackrock where it spread like wildfire and killed countless people in a plauge that lasted over an hour. This video shows scenes from the last hour of the plauge and the destruction it wrought upon the poor city of Orgrimmar. P.S. Not that it really matters, but all the times given are in EST..