Are you going down the tunnel and taking the portal past the new mobs there, or are you turning back around and clicking the portal where you zoned in that is the actual zone out for the instance?
I am unable to reproduce this issue. I suspect Taled is correct, as the entrance portal (the one with the three eagle statues) is the only one accessible at that time, and it returns you to Raj'Dur Plateaus. ~ Kaitheel