In a party we are not able to progress quests together. It’s a bit annoying that whenever I complete a quest, it only gives me credit, but if my friend is also in the party (and on the same quest), it doesn’t progress their quest. So meaning, we need to double back and redo the quest again, so that they can get credit. It’s quite a bit annoying.
This is for both campaign quests and for monolith quests.