Capped Stoneskin (max is 420 for Smn with Stone Gorget/Siegel Sash/Haven Hose) and Shell IV (Light Spirit) are essential.
I recorded a JoF fight and it was a tedious victory. I even used a Vile elixir because I was too scared of Convert. When he's in his closed form, his melee dmg is doubled or nearly tripled. Stonega III is survivable and Garuda (at 100% HP) lasts long enough if I'm petrified but I took none of these spells this time.
Spoiler: show
Anyway, also tried Byakko but lost, definitely feasible as Smn since now he is hitting for 40~70 dmg per hit and the additionel effect always does 0~2 dmg.
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