Prior to Cataclysm, Azj'Tordin gave players the quest Pusillin and the Elder Azj'Tordin. In the course of the quest, Pusillin would drop the Crescent Key, which was required to open doors towards and inside the Northern and Western wings of Dire Maul.
With the events of The Shattering, Azj'Tordin is no longer affiliated with the Shen'dralar faction (though his NPC tooltip remains unchanged). He does not give any quests, rep, loot, or dialogue. There is no point to killing him.