Ok so I really like Ahsoka and the nightsisters in general. Mind you I'm only level 44 and I'm only at 4 stars for just about everyone:
The reason I'm choosing Ahsoka as leader is because she's super slow and the turn meter swing seems really good on her. This comp has an insane amount of healing, single target physical damage, and two heroes with reliable evasion up on top of leader ability. Asajj is mostly utility with stun, special damage aoe and taunt removal. Anyways if there are other Jedi or nightsisters that would fit better I'd love to hear the reasoning. Or if Ahsoka's leader ability really sucks I'd like to hear that as well.
I realize Old Daka is a more reliable stunner because of her speed and has healing and ress capabilties, but because this comp lacks aoe, taunt really hurts its ability to get rid of big threats. Just my thoughts.