Originally Posted by
wooootles
Siege of Orgrimmar also had the most lore-affiliated bosses.
Fallen Protectors, Sha of Pride, Zaela/Galakras, Nazgrim, Malkorok, Klaxxi and Garrosh---that's half of the encounters having an actual reason why they were there in the raid; characters that you really hated and characters you were really attached to. Some were even developed during the course of the entire expansion. (Do you see Ultraxion as that one guy you hoped to face someday back in patch 4.1? nope)
Compare that to the other popular choices: ICC had LK, Sindragosa, Lootship, Saurfang, and maybe the Blood Princes qualifying as lore characters; the rest were just freaks inside ICC used by the LK to 'test' the players. In DS, only Deathwing (x2) was the only lore character you fight; you never heard of the rest of the Old God freaks before until DS.