I went pretty heavy into Phoenix when LSTB first released, and I still use them pretty extensively. They are my go-to squad for the p6 rebel mission, so I can save CLS and Zolo for the special mission.
They get dropped on defense for TW.
They actually beat the mythic tier of Military Might easier than cls/zolo/chaze/random 5th.
They have two of the best ships in the game imo, and easily the best reinforcement ability on phantom.
For the record, I have g12 zKanan, zZeb, zEzra, and Chopper, and g11 Sabine & Hera. I'll be adding Sabine and Hera zetas shortly and taking them to g12 also.
You pretty much have the correct zeta order already imo. Kanan, Sabine, Zeb, Ezra, Hera would be my recommended order unless you are using Ezra with Jedi.
Hera's zeta seems very weak, but when it is used properly with zeb it adds a ton of DPS to your squad. Use Zeb's staggering sweep, which will give him 50% TM w/ 5 Phoenix +20% from lead for an almost immediate turn. Use his basic to stun that toon, then call him to assist with hera's special and he will daze or stun another enemy and gain 50% TM for another almost immediate turn where you can use his Sweep again. I have had crits with Zeb's special for upwards of 60k damage against buffed, non-debuffed enemies ( the ideal target for his special).
With Sabine's zeta dishing out stagger and exposes everywhere ( both of which allow a stun with Zeb's basic) , Zeb's TM train can very quickly shut down a large number of enemies, which is ideal for TB or assault battles.