Well i was aiming simple, but if team actions could be traced, that would be amazing. One of the best decisions I've seen in gaming in a while was the decision to base the scoreboard in Bad Company 2 on team points, rather than kills. The developers gave different point values to different actions, incentivzing heavily actions that would lead toward team play, while still giving modest points for kills- which are necessary after all. I think it's one of the reason that in a fast paced action style FPS you see some of the most co-operation from total strangers. Of course there's always that round everyone goes recon...
At any rate, I know CRPG is nothing like BC2, but the concept is the same. Give incentives for desired behaviors and players will trend towards those actions. Assists, Gates Closed (Defense), Gates Opened (Offense), Objectives Captured, Total Damage, etc would do wonders towards convincing people that perhaps banding together is a good thing for everyone involved. Intentional harassment could be disincentivized by removing double the amount gained for negative team actions Team Kill, Team Wound, Gates Opened (Defense), Gates Closed (Offense). Even if players did not care about these metrics, they would provide an easy way to track and separate consistently malicious team hindering players from those who are merely having an off day, or just being a whimsical trickster on occasion.