Group quest phasing issue. All quest phases should be synced to the party leader. If a group member completed the quest already, don't give them full xp upon completion (if thats even a concern).
Additionally quests that have have interaction steps should not require the entire group to do the step. Like in the burning town missions, why can't your party split up and put out the fires faster (which would make wayyyyyy more sense).
My comrades have returned. I erect the spine of gratitude. You are a hero today. - Bura-Natoo