Are nightsisters viable in current arena?

Absolutely

I'm not a competitive arena guy, but based on the amount of "Omg nightsisters are teh OPz wtf devs" threads since Zombie was reworked, I'm gonna go ahead and say yes.

There’s one guy on my shard running MT lead, Asajj, Daka, Zombie and Spirit who can take first place.

Mother talzin, daka, ventress and zombie are key in the team.
Ventress z unique is mandatory, daka unique is so good for raid (but not needed in arena) u also need talzin leader Z for arena and mostly talzin unique Z...
Then un can use as 5th spirit, taila or whatever... But they all G12 or g12+
With good speed mods and smart decisions controlling them in attack u can crush everything, so definitely NS are good in arena

Ever since I figured out the right rotation, I always beat ns with my zep.

Nothing can 'hold' against anything really, but you can climb pretty high with NS now.

if there's a light side meta. NS can probably be the anti-meta.
and as anti-meta, they fit in the current arena.
there were so with JTR, got pushed aside by the sith, and now they can beat revan and bastila and therefore, they are very viable. however, will probably be targeted on defense since the revan meta is kinda small, only number of people have. most still use Sith, and they enjoy fighting those NS.
so you can climb to top with NS, but i would recommend to swap to more defensive team after.

There are a lot of NS teams in the top 50-100 area of my december 2015 arena, probably a reaction to the Bastila jedi teams as they seem to eat them like crackers.

I run a NS team and can hold in the top50. I can beat most types of teams on any given day but do struggle against Strong Traya and Revan teams.

"DaPowerfulJedi;c-1681435" wrote:
There’s one guy on my shard running MT lead, Asajj, Daka, Zombie and Spirit who can take first place.

Then you are in the worst shard known to mankind. A trooper team with veers zeta and a slow + 110 speed range trooper destroys NS every single time. Troopers can try to lose and cannot.