Quest log tells me to “Talk to Khadgar in Dalaran to set of for Khaz Algar”. I have talked 3 Different Khadgars and none of them send me to Khaz Algar. The one next to Magni just has “(Play Movie) Remind me of the events so far”, the one in the upper room with Jaina has and “Can you tell me more about…” and Khadgar in Dalaran proper just has some old quests.
Are you at the point where you need to click the portal to turn in the quest?