A team of well—geared characters with synergy underperforming? My first thought was that it would be a standard case of poorly modding. And yes, you can gain a lot from sorting out your mods. F.ex. Han scores a lot if crits due to his crit chance up buff. He should have a crit dmg set and crit dmg primary triangle mod. Furthermore he's a damage dealer and should have an offense primary cross. With his current mods you don't use him to his potential. And...potency sets for CLS who has that high potency bonus from his abilities? Furthermore, you would want your R2D2 very fast for an early smoke screen and with high protection/health to boost the bonus he gives through number crunch zeta. The circle mod from ST Han should definately go to R2D2 instead.
You can improve VERY much simply by moving the mods you already have around.
But ok, assume that you've focused on farming veterans instead of mods, and that gave you JTR, which is really well done :—).
The filtering option on swgoh.gg is a great tool for sorting your mods:
https://swgoh.gg/u/onlyzuul/mods/?stat1_16=1
https://swgoh.gg/u/onlyzuul/mods/?slot_5=1&stat1_56=1&stat2_5=1
https://swgoh.gg/u/onlyzuul/mods/?slot_6=1&stat1_56=1&stat2_5=1
Good luck.