As title said, you need a lockout that has reached shadowlord iskar. Jump off the ledges circled in either of the two locations. It's seriously simple as that. Just make sure to use something to prevent fall damage.
They didn't have any sort of death line when I was on the 6.2 PTR, so there's no where you really can't go that I'm aware of. The walls of HFC below you are not solid, so you can walk through those.