Here are a few of my ideas:
-Give the ability to the person who gets a team mission to assign someone else to complete it, NOT just the person who got it.
(Ex: The person is to afraid to go up and grab the item so he runs away and leavs the group even though he just leveled and wouldn't lose any xp if he died anyway.)
-If the person who held the mission is removed/left the group, give it to another person in the group so it can be completed.
(Ex: Member goes linkdead and doesn't return, no rewards)
-If someone is attacked on one floor, and goes to the next, cancel the agro so they can be healed or allow it so team mates can heal with packs and not just nano's on the floor and not themselves.
(Ex: "You guys just go up and take the agro and i'll wait here for you to finish the mission because I can't heal")
-Fix the problem with people dissapearing from you screen and cannot see them until you zone.
(Ex: You can't see them, but if you zone you can see them just peachy.)
-Once the elevator/potal is found, make it on the damn map. If you must include it with one of the map upgrades. Even make it its own upgrade if you have to.
(Ex: Run around for 5mins trying to find the lift after completing a 4 floor mission)
I can't think of anything else to add... . enjoy.