2 roaming thieves
http://metabattle.com/wiki/Build:Thief_-_D/P_Roamer_
the play with your friends build for thieves..
Crystal Desert
One power, the other condi build. People usually can get away from one type of dmg but when they have to fight both, it’s very difficult for them to survive. The power thief would be perfect with d/p, easy access to stealth for both of you.
Underworld Vabbi 1.5yr
1 Thief is High Critical Power Build, for the Direct Damage Bursts.
The other Thief is Condition Build with Venom Share, so that the second Power/Crit Thief can deal also some more Conditions on the fly to support the Condi Thief with more Stacks of Torment, Chill, Poison ect.
Personally I like the idea behind sub classes ~ quoted from Chris Whiteside