Hi. I would like to share how i managed to interact with Taeran Fordring to start the escort quest.
What you need to do is to take off your disguise in the room in front of him. Then the 4 elites around will jump on you and kick your ass (you need a friend abble to ressurect you or a Ankh or a soul stone).
Taeran will jump in to protect you and fight the 4 elites around him. When he finally kills the last one of them, he will start moving back to his spot. You can interact with him and pick up quests from him during the time he's running back to his position after a fight.
Ps. If you started the escort and your friend wasnt abble to pick it up, he will be abble to pick the quest later on while he's fighting mobs in the castle.