Ok, my other two contributions sucked, as one was a repost and the other was me trying to steal rep. My apologies. This time, I have a real exploit though. This can only be done DIRECTLY after the Gunship battle in Icecrown citadel.
As we all know, the jet packs from the gunship battle dissapear shortly after the ship docks. However, as you near Deathbringers rise, use your jetpack to fly over there. Keep using the jetpack to remain airborne, and head towards the door. The top right corner is where I tried it. Once I got there, I was stuck, and my jetpack was disabled. I moved around and then I fell down. I was in the door. I walked towards where the inner spire portal would be, and what do ya know, there I was, in the inner spire.
If this doesn't work for you, well, thats your bad. You only have one attempt to do this per week, and you need to do it fast before you lose your pack.