This has bugged for me too, twice. (First on Sunday, then today.)
Both times Trahearne died multiple times. One of the big issues is that the Vigil Sylvari who accompanies the player and Trahearne pulls EVERYTHING, making it very difficult to control damage, so Trahearne dies. A lot.
One of the other things is that once you have to start running up the hill to the first camp of researchers, Trahearne and the Vigil Sylvari stand and fight the hoardes of Risen, which keep spawning, and never run up the hill with you. This means they inevitably die and just respawn at the top of the hill when you get to the top to fight off the Risen with the Asura.
The first time the quest bugged for me, only Trahearne followed me. The second time, about 3 other NPCs followed me, some from the second, some from the first research team. It seemed the ones who walked back into the room where the second team were hiding out were bugged, whereas the ones that stood just outside the enclosure followed, but only to attack the Risen Grubs which spawned. The second time, I cleared the entire cave before triggering the rescue.
Both times I submitted a bug report and screenshot in game, so I do hope the information helps you guys. I really want to make it to the end of the game but just doing zone completions in the meantime is getting a bit stale ;_;
