As a droid fan i will tell ya that teams i had chances of losing to are phasma/daka/rg/jawa those stuns render droids useless.
Since anikin rework i am struggling with anakin and rg teams...
I typically use max lv
Hk g8
86 g8
88 g8
GG 5* g8
JE 4* g9
In top 50 daily sometimes top 20
Also swap GG for lv 80 g10 IG-100 sometimes.
I use grevious when there is a rey, yoda, doku or fives in party since his basic hits through foresight and cant be countered.
Overall JE is not OP since he doesn't actually attack anyone. His bombs are pure luck mostly and are better served to increase 88's attacks.
JE is 100% support.
If you want to beat droid teams with JE then kill JE 1st. Mine barely has 14k hp at 4* lv 80 g9, its not hard at all.