Just tried running a TBM heroic (In Defense of Health) and had most of the tasks complete, then died on a stupid pull. When I try to get back into the instance, I get the message saying "The way is blocked to you. Perhaps you would be able to enter if there was a reason to come here. " Server is Rathe
if im right, you get to a point where the task locks if you die after this i dont think you can re-enter will have to start over again.
Also, if no one is in any given instance for a certain amount of time, it will collapse and you're s.o.l.