I like this idea. However, to avoid making them too similar to a rogue with a load of anguish feats I'd give them pain points. When they attack they can spend pain points as a free action (this can also be done on an AoO) to give their attack some extra power.
1 pain point: tears in enemies eyes, -5 penalty to spot checks, grip on weapon loosens, -2 damage for 1 round
2 pain points: cries out in pain, cannot talk for 1 round, heart misses a beat, shaken for 1 round
3 pain points: becomes scared of Mord'Sith and must make a will save to attack her for a number of round equal to her wisdom score, leg muscles weaken, speed drops to 10ft for 1 round, cannot take 5ft steps
Ect.
How they get pain point is up to you. They could get them like inpsiration points at the beginning of the encounter, they could have an infinate number but need to loose 1 hp per pain point spent or gain a flat amount per attack (same amount as a rogue gets sneak attack)