[Aeternis]

Quests on your Campaign tab or specifically marked as Group are the only quests which will complete based on group kills or looting. For drop-based quests, everyone needs to loot the mobs, as the items are not automatically distributed. So, to answer your question, you need to complete Work Order or non-campaign quests individually (you can do them as a group, but will need to work towards completing everyone's totals, ie keep killing Brax until everyone has the number of skins required to complete the quest)