It's quite easy with zFinn.
Start battle with Poe and AOE Expose, then hit with expose inducing abilities (Finn, RT, Poe) or stun droids (R2). Keep droids dead or stunned as best you can to minimize assists and dispelling.
Prioritize hitting an exposed enemy over anything but stunning a B2.
If you are close to finishing a round (1-2 toons left with below medium health), do not use Poes AOE Expose, so you'll have it ready for the next round.
Remember to use RT's dispel on the droid when they get the ridiculous defense up buff in later rounds.
I did regular with:
(L) G8 zFinn
G10 R2 zeta on number crunch
G8 Poe
G8 RT
G8 Rey
In the bonus round I failed first try with the same set up, and made it in the second try with:
(L) G8 zFinn
G10 R2 zeta on number crunch
G8 Poe
G8 RT
G8 BB-8 (Only 5* and lvl 63, no mods, abilities only at lvl 3-ish).
I saved Illuminated destiny for the last round, but could have used it one more time along the way I guess.
Rey instead of BB-8 would also have been more than possible, as my offensive strategy was very faulty on my first try.
See my swgoh-profile for more levels, mods and abilities.