Frost mages are getting stuck on this quest and this is the way to fix the problem. You need to get to the version of Deadwind Pass that no longer has Dalaran floating above it. In order to do that, you have to complete 3 quests. Go to the Dalaran above Broken Isles and talk to Archivist Elysiana in The Violet Citadel. She will ask:
Do you wish to hear a tale from the past, Player?
and you reply:
I want to experience the return of Magni Bronzebeard and Khadgar's adventures in Karazhan.
You receive the quest: Calling of the Council
Take the portal to Stormwind (or Orgrimmar for Horde), then take the same portal to the Dalaran over Deadwind Pass that you took for the quest In the Blink of an Eye. Talk to Khadgar outside the Violet Citadel and complete the quest. At that point Brann Bronzebeard shows up and offers you a nice little side trip to Ulduar:
The Diamond King
When you're finished in Ulduar, you take a portal to the front gate of Karazhan. At this point, if you look up, you'll still see Dalaran above you, so you're not where you want to be yet. Turn in the quest and pick up:
Hiding in the Stacks
When you finish in Karazhan, Khadgar will port you to the Dalaran above Deadwind Pass. However, when you turn in the quest, the game will reload and you will be in the Dalaran over Broken Isles. At this point, your problem is solved. Just take the portal to Karazhan in the Chamber of the Guardian. Dalaran is no longer over Deadwind Pass and the Abandoned Kirin Tor Camp is properly phased to finish The Deadwind Site quest.