Bleh, finally took down Caius. Discussion with Djinn suggested that I just wasn't working enough support in, so I went from my usual A team to a... weird setup.
Relevant XIII Synergy: Evil Pumpkin, keepsake knife, Vega 42s, Wyrmfang Rod, Physician's Staff, two armors
Locke (Valiant Strike) Dismissal/TreasureHunter's Raid
Leon (Hand of the Emperor) Indoor Spell/Banishing Blade
Tyro (SG) Saint's Cross/Fullbreak
Vanille (Oerba's Boon/Miracle Prayer) Shellga/Curaja
Fran (Shatterheart) Magic BD/Power BD
RW: Shout
Yes, Fran used my 5+ staff as a melee weapon. Also had similar attack to Tyro using the Vega 42s. Also was taking the place of Agrias using basically a weaker version of the same SB.
Otherwise, HotE was another mitigation layer, so waiting for Oerba's Boon to put up protect was mostly safe. Although worth noting, because Leon is still without MC2 , one run with mostly the same setup failed because he died before dispelling a Regen late in the fight, which let Caius live long enough for Shout to wear off at which piont I couldn't even OUTPACE said regen. So he got that new HP boost accessory from the event, which solved the problem handily. Doubling down on attack buffs also proved vital because while I have a lot of XIII synergy most of it is ancient (or mage gear). Also meant that Leon was adding that damage lost from not bringing a second SSB user.
but mostly the takeaway is that Caius lost because of the efforts of a bunny girl with 7000 damage staff thwacks.