I set Zbossk, Boba, Greedo, Dengar and Zam on Defense last TW. It held for 11 battles.
I also beat the 7* Chewbacca event with this team. zBossk G11, Boba G12, Greedo G11, Dengar G10, and Zam G10. They also do well in Phase 2 of the Sith Raid.
The Bossk Zeta was nice because it let me mod with Protection Crosses rather than Potency (used under a Boba Lead), everyone survived much better with this make up.
Zam's abilty to pop detonators with her basic and go again seems more beneficial than using Cad Bane, but it depends who you are up against I supose.
Embro, Aurra and Jango are on my to be farmed list. They all seems strong and I will eventually have 2 bounty hunter teams.
I am not using IG-88 with my bounty hunters since I geared up Bossk, currently he leads my Geonisians for a back line defense squad in TW, he also synergizes well on full droid teams, with HK lead.
Dengar is a solid counter to R2-D2 teams as he can prevent stealth.
Greedo does great damage with his ability to go again on a crit (recommend stacking over 60% crit chance), but in phase 3 and 4 of the Sith raid this can ad a lot of stacks to Treya's buff very fast, so be careful about that.