So nightsisters in a nutshell. A zombie that cant be killed, a ghost that gains evasion all the time, 2 toons that only get stronger with every enemy/ally defeat and revival and a witch that inflicts plague and temporarily revives allies. While asajj gains offense for defeats (and revivals?) and daka gains health in the same fashion I think spirit is probably the best. The frequent evasion gain makes her the hardest of the squad to hit and she deals quite a good amount of damage at relic 2. In fact yesterday she was the only nightsister besides zombie who was still standing and at full protection and health even when sidious opened up on his aoe attack thanks to her evasion. She can stun and remove buffs with her special attack which is nice but for anyone who has her at relic 7 how good is she.