First off, I don't know if this has been posted before, but I'm going to post again away.
I have an idea for an item that isn't NEEDED but would make teaming more effective/easy:
Aggression Detector: When in a team detects what the current fighting targets aggression is aimed towards.
Basically, something that detects who in the group has aggro on them. This would be extremely helpful for the healers and the tanks. Instead of constantly watching the team health window or trying to read the same colored text as the mob switches from player to player to see who it is attacking, a person with this item equipped would see in red text who was being attacked (EI after mob switches to Cyronic chat window would send a message "Cyronic is being attacked!!")
This helps out greatly because Healers see who needs healing immediatly, and tanks know who to get the aggro off of. Of course that's a bad tank if you can't keep an aggro :P
Just a thought.