Background: I got a PUG together last weekend and we did most of the "The Shattered and The Lost" mage quest in Craglorn. The group fell apart right before facing the final boss, The Lost One. I tried to run it solo, but just couldn't hack it. I really want to finish the quest.

Which leads me to many questions: Are theses group-quest dungeons in Craglorn public or instanced? If public, I can just go back and wait around for a passer by to help me out. If they are instanced, what can I do? If I group up with someone without sharing the quest, will they even see the boss, or will they be out of phase with me in the dungeon? If I need to share the quest, can I do it with someone who has already completed the quest? Or do I need to find someone who has not yet completed it? Help! I'm sure I'm not the first person in this situation. How do people solve it?