That simply cannot be true. What do you mean by you "checked"? How? Either you've taken a year out, or he sat at level 27 (I think your shard is assigned at 28) for a year.
Ignore the total GP. In squad arena only one thing matters, your arena team (and their mods obviously). Those with more GP could also be carrying a lot of fluff in their rosters.
If this is you: https://swgoh.gg/p/911278523/ I'd adjust your team. You don't want Traya on the same squad as DR. She cleanses his Ferocity, and if he isn't in the lead slot it only gains a limited amount of it. I'd try DR, Badstilla, HK, Mother Talzin and NS zombie from what you have geared. Or GMY and Thrawn as 4th and 5th.