Today, after several close attempts, I finally downed the third boss, Norushen, in Siege of Orgrimmar. This boss requires near-perfect coordination across the raid, as well as personal responsibility from all players in all roles. I, as well of the rest of my guild, am very proud to have progressed past this milestone.
When the last player in our group was finally dead, the boss had a mere 0.17% of his total health remaining. This was the closest attempt, barring the one successful kill.