I’m having the same issue. I’ve attempted the scenario 4 times, luckily the last time I was stuck again (as was another group member) but the other person solo’d the whole thing and fortunately it completed for all of us.
I tried reloading UI, relogging, restarting game, none of those helped.
I tried dying to rez out of it, it won’t give the rez option so I had to drop group.
I found I could Fel Rush around and even attack mobs, I just couldn’t move any other way and I was running on the spot in mid air.
In one group I tried, someone used a Swapblaster on me, this put me on the ground but I was still unable to move.
Attempting to relog gets you the error message, “You can’t do that while jumping or falling”
Attempting to port out of the instance gets you the error message, “You cannot do that right now” (or something to that effect).
In each different group I tried there were a variety of different classes, races and levels. I don’t think those have any bearing on it.
If you can find a group of people who are sympathetic and happy to carry you, just hang in there (no pun intended) and it will complete.