I just did that one and it was kinda tough. You just have to keep upgrading your ships and pilots until you hit the tipping point where you can take out one opponent before or right after they get their first reinforcement. If they achieve numerical superiority you are screwed.
I used:
6* X-Wing 7* Biggs
5* Fighter 7* Consular
5* Ghost 5* crew
4* Phantom 5* crew (4* Sabine)
4* Umbaran 3* Fives (but G8)
Also cunning, guile, go faster stripes and fuzzy dice in the cockpits. (Just kidding, though I have defeated fleet arena opponents with up to 25% more GP than me)