FIN-TS Twilight Frontier Full Garrison

You can probably get away with any vanguard, though Myrtle is the best since you just want DP.
Ptilopsis, Eyja, and SA are pretty much required for this.
Ptilopsis due to being an AOE healer and the +range on s2 is necessary to keep Eyja alive.
Eyja/SA to kill the strong enemies. Maybe you can replace SA with another strong ranged melee dps. Thorns?

For Kroos/Ash, you can use pretty much any two anti-air snipers with decent dps. They just need to kill the Sarkaz Centurions, and are given plenty of time to do so (as well as help with the drones, but those are weak).

Blaze can be replaced with a Defender, the only requirement is for them to survive.

Nian is very useful since she makes dealing with the last hero much easier, but since you can replace Ceobe/Mudrock/Ch'en with whoever you want, you can probably find another way to deal with him. Surtr will probably do it. As you can tell, I didn't handle the last hero very cleanly, and I was too lazy to redo it.

3:16 - you can use pretty much anyone here to help kill these guys, or you can just use Pallas's skill. If you do, you'll have to use someone else to deal with the following enemies.