Yes I'm sure someone said it, but if you hit the mob and it dies without resetting, regardless of your group affiliation you should get the quest completed. Drops should go to the group/person that did the most damage though. But if that drop is a quest reward, everyone that hit the mob should get it. No sense in level 130 players still yet to complete a level 60 quest with the current system. It is ridiculous.
Target lock should address this concern in update , I don't disagree that people should be able to complete quests if they are willing to put in the effort . My only problem is the people that want everything handed to them this sense that they deserve it or are entitled to it .