Mercurial Gauntlet Wind:
Lv30: Assisted 2x Auto stops being reliable, so I switch to Manual.
Lv35: This isn't going to work much longer, so I test and find that I need to wear 30% Prep in combination with 10% Helper Prep to get in two Dragon uses.
Lv38: Now I need to start optimizing the fine print. For my composition, that meant using specifically Shapeshifting to I-Frame the first clap, and intentionally get hit by the second clap. This triggers Last Offense right before Break, and lets me get second Cerberus before Break expires.
Lv39: Sweet, Sunlight Stone!
Lv40: Cleared with 0:06 remaining on first clear. Epithet is still Gold, if anyone is wondering.
There's certainly room to optimize damage in my composition, but here's the 22k Might team I used to clear:
(Sorry about the formatting, I use an Android app for the Imgur uploads)
Marth: MUB 5* Elemental | MUB Cerberus | Shining Overlord/Stellar Show | 2997 Str
Vanessa: MUB Anti-HMS Void Elemental | MUB Ifrit | Kung Fu Masters/King's Countenance | 2232 Str
Bow Ezelith: MUB Anti-HMS Void Elemental | MUB Ifrit | Forest Bonds/King's Countenance | 2007 Str
Xuan Zang: MUB Water 5* Elemental | 1UB Agni | Resounding Rendition/Dragon's Nest | 1899 Str