We will be working on queuing loot in the party properly. For now the loot is taken by the person who has made the most damage to monster if I'm not wrong. We will also fix the problem with the task in near future.
Thanks for your report.
As i played few last days in role of tank, observed that i dont get any loot from party play (don't know if most dmg get loot or killer), and if team-mate dont have same task i dont get kills count unleass i kill creature.