Jean, I know that going public groups other players who are on the same general quests as you with you...no asking.
Hubby and I discovered that to play with friends you needed to add them to your friends list, then right click their name and invite them to play. The one time we did it, I invited Soot so we had my quests....not both his and mine. But we could play together cooperatively and we could trade items and gold. We also discovered that when playing together, your loot was only visible to you so no worrying about "Stop picking up all my loot" like some of the games we have played together.
We have not been able to play since (life is Not cooperating with us) so that is all I know.