Snipper / Soi Team Comp
Ring of Earth
Ring of Speed
A.Snipper is the preferred damage dealer & A.Soi is the preferred Support. Storm Wings Sky-Splitting Earthquake skill removes all debuffs including Rachel's. This makes Passive damage increases (like Ace) very good for this boss. Storm's Breath decreases your teams attack by 80%, Heroes that give immunity to Attack debuffs (like Soi) make this boss a lot easier.
The last effect to worry about is SW's passive which reduces buff duration by 1 turn with each normal attack. Petrify resist accessories are recommended for this fight even with soi's 6 turn of petrify immunity.
Soi, Jake & Cleo have petrify immunity for all allies. Soi is a better alternative then Jake, and Jake is a much better alternative then Cleo.
Another strategy for dealing with SW's debuffs is using Elysia who gives all allies debuff immunity for 2 turns & debuff immunity 2 times with her Awakening Skill. SW reduces buff duration however, removing 4 turn debuff immunity quickly.
Currently The best way to deal with SW's debuffs without losing out on DMG output is to bring Soi (Petrify) & Petrify resist accessories.
For decreasing SW's defense you can either bring Ace or Yeonhee who doesn't waste time using a skill to decrease defense along with rachel
Skill Priority Your Skill Priority should be: Apply Rachel's DMG recieve debuff, Spam Snippers Skills, Apply Rachels decrease DMG after snippers VS's are gone then use Soi's A.Skill to amplify attack.