In GW for the last node I faced:
Gen Kenobi (L)
Barris (Zeta)
Anakin
5's
Aayla
It was terrible.
That is a hard team to beat, no beans about it.
I didn't even realize Zeta had her Barriss until after hitting Kenobi with 19k damage (TFP) he lost barely any health. I thought he must have a monstrous health pool or something.
Honestly though, it isn't just that toons heal 20% after every crit, it is the fact that she cleanses one toon at the end of every turn.
It is really tough to get healing/buff immunity or shock to stick for more than one turn. If the toon gets cleansed and gets hit with a crit it literally undoes the progress you just made.
I was able to use Palpatine, TFP, Shore, Boba, and RG to knock out (barely) Anakin and Kenobi before my squad got rocked.
After that I had to try several different teams just to be able to take out Barriss. The others would have been nigh impossible to take out otherwise.
I don't have B2 or any Zeta's yet but I have most every other toon that people say can counter it. It is doable but very hard! I do not think I could do it with a single team. If it weren't a GW node I would have been up the creek.