alot of people have left Oregon's team quest. Randy is training in Vegas. Even Tanner is basically training wherever he can find a spot. Hendo has his own spot in Temecula now, and Linland is training with all sorts of different factions.
This sometimes happens when guys need a change of scenery or just need to learn and work on new aspects of the fight game. Same thing happen with Team Punishment, now slowly but surely all those guys are getting back together. I'm sure it was nothing personal between Leben and TQ, just a matter of having quality training partners and and having a more well rounded fight game.