1. Full team
2.
A. Team consists of one person distracting the outsiders (puppies, humbug, etc...)
B. Team has a poisoner that can kill/block all healers
C. Team uses pets often (maskerwaith's hexing haze, drakon's firestorm, Seraphynx's heart attack)
3. Best weapons for this mission is/are: Note that 5* or lv. 10 4* is most ideal)
Swords: Warmaster Rocket Hammer, Acheron (Obsidian Edge), Divine Avenger, Gran Faust, Combuster, and Flourish
Guns: Grim repeater, Blitz Needle, any Antigua line, Drivers, Winter Grave, and any Blaster line
Bombs: Dark Briar Barrage, Venom Veiler, Stagger Storm, Ash of Agni, Crystal/Dark Matter bomb, Dark Retribution, Vortex bombs, Voltiaic Tempest
4. Sparks are not as expensive than energy for 50ce, so best to stock up on them.
5. Hearts are scarce, so it's best to get the capsules from the merchant, and (for anti-resist users) antidotes
Personally, it's best to bring a final flourish, a lv. 10 elemental weapon, an elemental shield, and ele/shad resistance.
If I didn't have another different mission then Gremlin Assault!