FoK was a gimmick against all/mostly caster compositions.
It is still an ok method to spread your poisons across a group.

You have the option of Combat for Killing Spree + Blade Flurry, which should destroy 1-2 toons in close proximity.

Mutilate/Preparation is probably a better build; you don't need to be behind them.
With Cold Blood, that's 8 automatic critical hits on one target.
And four combo points per rogue.

You apply Crippling, Deadly or Instant, Mind Numbling and Wound Poison to anyone you attack.

Cloak + Vanish, will let you reacquire stealth some of the time.
Dismantle destroys melee opposition, and you'll have this on round robin.
Blind is a very strong CC, provided your allies don't break it.
Between Kick and Kidney Shot, casters will hate you; possibly the BE silence too.

Definitely a lot of toys and burst.