I eventually did it with zFinn g8, Rey g10 and Chewie g8, after a hell lot of failed attempts. Mainly, Finn died too quickly, I wished I had had g9 for him.
The omega on his special is very helpful, to make it more likely to stun opponents.
First of all, make sure you go without any cooldowns from stage 1 to stage 2. The cooldown reduction on Finn's zeta may come in handy here...
Then, in general, stun the riot control stormtrooper with Finn, remove the taunt from the FOST (and inflict speed down on the rest) with Chewie's special, and try to kill the FOTFP's/officers first and asap with Rey.
If anyone dies in stage 2, I guess it's better to retreat and repeat.
