Bonding with Tio pays dividends here. His defense is incredibly high; most physical attacks will barely scratch him even with a buff. However, Omega Strike II completely nullifies enemy defense in this mod. Cold Gehenna makes a return here as well since the dragons have the same status vulnerabilities (different elemental efficacy though).
Estelle rounds out the group with Morale - seriously, the rework makes it insanely good - and Hundred Blows to push the boss back and potentially faint him. Even without the status proc it helps to knock him away so he can't target the back line as easily. He does still have ranged attacks though, and his Hand of Lightning has a weird property that makes it hit multiple times sometimes...but only if he's hitting multiple characters. Burning Finger is as strong as ever but it seems to have a strange effect as well: it doesn't charge your CP at all when it hits you.
Pretty damn tough fight. This one took a while to succeed at.