Chopper is essential to Phoenix Squad

PowerMaster

Phoenix Squad begins to really become a power after 4 rounds.
This allows Ezra's shared unique to maximize at +40% offense.
Kanan's high counter attack and crit rate helps debuff enemies offense -50%
I have started using Hera and Ezra assists on chopper at beginning of fights. Even though chopper's attacks are weak and assists can be very effective when used with Zeb (Daze/Turn Meter control) or Hera (Expose combos) The buffs / cooldown reduction chopper applies to team mates are worth it. Offense up +50%, Defense up +50%, speed up +25% and cool down reduction chance 60% apply each time chopper attacks or counter attacks.
Here is why Zeb's protection up that can give retribution also helps.
Reducing cool downs allow you to use special abilities more often. (Don't forget that Hera's unique give 20% turn meter when specials are used (40% if under full health)
The turn meter gains and potential speed up buff begin to make each characters turns happen quicker and quicker. (Automatic health and protection gains each turn)
Add this to healing up to 25% when you get debuffed gives something that impressed me with Phoenix Squad. I would run them on AutoBattle in Galactic War and just watch the battles. (At first it was somewhat stressful because you watch as one of your characters drops lower than 10% health only to not only fully heal quickly, but also recharge protection) Next battle you start with full health and protection.

Phoenix Squad also does well against AoE enemies that debuff. Somehow my Phoenix squad (4-6 stars, not all completely leveled up (levels 70-82) easily took out an Emperor lead team that easily wiped both my empire and main Jedi teams)

So early survival in battles (if you are able) makes all the difference.
Ezra unique + frequent chopper buffs can yield +90% offense.
Kanan debuff (-50% offense) + frequent chopper buffs (+50% defense)
Protection up when damaged
Healing when debuffed
Team set up to maximize protection (zebs unique adds 40% of your health as additional protection)
Frequent protection up buffs (50%, 40%, 40%)

**One death substantially weakens Phoenix Squad and usually battles go south very quickly once one of your characters dies**