For ships, try to use those ships from characters you are going to use eventually. For instance, I am farming both phoenix ships, Biggs ship and TFP ship mainly plus Vader/Boba ship when they rarely appear.
I guess your problem with arena comes from mods and stars, are you sure you are refreshing cantina energy at least 1 per day? At level 60 I had my whole phoenix squad 6*, Zeb 7* and with 5 health mods dots. If you want to improve in arena level up all of them to 5* and spend one week and a half or so trying to get tier III health mods then return to Hera/Ezra farming. Mods make the difference in arena.
Phoenix isn't weak in arena till end-game, I have seen many people lvl 75+ who still use phoenix squads. Max the whole squad to 7* and push their gear to VIII-IV (You can push Ezra to X) before making any transition.
