Here we go:
Option 1, split Nightsister and Jedi.
Ahsoka lead, Daka, Asajj, Luminara and QGJ/Talia/Jedi C . . .
At earlier levels you may need the extra heals from Luminara so you can withstand the longer battles. Ahsoka is very reliable too, she effectively takes care of herself due to her heals and occasional party heal.
Personally, I've been using Ahsoka, Asajj, Daka, Talia, Luminara.
Option 2, full Nightsisters.
Asajj lead, Daka, Talia, Acolyte, Initiate.
This team requires user control to be effective, if you have another team it is best to set them for defence in Arena, especially now that you will ve able to see the entire squad in Arena now.
Full Nightsisters will give you: stun X 2, party heal X 2, self heal X 3, enemy party buff removal, enemy buff immunity, stealth, enemy party turn meter reduction, party turn meter gain, revive, party debuff removal.
I can't think of any synergy with that many abilities. So this is a very technical squad, one that takes a while to get used to and to play properly. Unfortunately, AI is useless with it.
I think that Initiate is probably one of the most under rated heroes in the entire game. She has the second highest health, second only to Bariss at gear 8. She crits a lot and could work very well on a lot if teams,for example Sidious lead.
@Plasmaj
If you do use Phasma as lead Asajj's Rampage is often wasted on opponents you don't want to use it on. Calling in a 6K crit on an opponent with 1K health is a massive waste and quite often happens when I borrow Phasma.
Upcoming changes: Talia is getting a massive buff, Asajj is having her party heal upon debuff removal switched to an individual heal, health steal is being fixed. This will mean that Talia will be a lot, lot harder to kill. Her heal will be even more reliable so you can use it more often. Asajj will also be more resilient as her health steal stat is great.
So one negative, two positives.
Extra for experts: if you can't switch to another squad for defense set Talia as you leader. At level 6 She gives Nightsisters 15% evasion, on evasion they heal 5%.
This evasion may win you a match on defense, speed most likely won't.