Pretty bad idea, as this would either lead to sniping and kicking the players until you have the correct match and even more players quitting the game. In addition why should you be forced to play with random players if you have mates?
Yes, I`m aware of this situation, just say... why this method was working in several MMOs while in TERA doesn't.
that because the game developer was very lazy to maintain their player behavior, with using any method to prevent this and there.
My conclusion is, you can create any method, but the point of any MMOs `Purpose` is the community itself, while you running a dungeon with many people, not what TERA did, running a dungeon with the same `static` team.
Why on earth FFXIV with shit combat system but can become successful number #1 MMO in the face of the earth, (IGN say this, not me), while TERA with an outstanding combat system can`t? that gonna be a huge margin to resolve, and game developers need to blame.
And again, I`m not trying to argue everyone here especially veterans and pros,
and I want to memorize how fantastic the 10-man TERA dungeon is, while TERA in the current situation will never implement it forever. 
