I would argue that a MMORPG does not need to "encourage" team play (what you really mean is force it). Some people like to solo, some people like to team. There are people who like to team but have limited time to play occasionally and want the option to solo but play "around" their mates.
It's possible to encourage team play without requiring it. The way the game is setup now there is no real incentive to play on a team (except for the STFs). Missions generally take longer and don't give noticeably better rewards (you get more kill XP, but kill XP is laughable). Plus you have the added difficulty of finding people of similar level who have the same misisons available (unless you want to grind DSEs or Exploration missions)
As a counter-example consider City of Heroes. Soloing from 1-50 is perfectly viable but so is teaming. When teaming you can do missions belonging to whichever person you want and everybody gets the same XP. Due to the way kill XP is balanced you tend to level faster in a group giving incentive to group without requiring it.
LotRO's Skirmishes....easily soloable, but way funner with a group. Since everything in game is instanced, make it scalable by group size.
Add in a badge type that only drops when grouped, that can be traded for team type gear (maybe buffs for others, etc.)
So if you want to solo, great. If you want to group, great. Both should be valid play styles.
Yeah I never said require team play. I agree that with more risk comes better rewards.
So perhaps players that want to succeed should find players that like to succeed and players that wanna solo and do there own thing shouldn't do marks of honor or valor runs. As that requires you to have some knowledge of how to actually play as a team verses what they have seen in old episodes and movies.
And Barry would be proud to know Cryptic's whole problem is Bushes fault..