Some things I can make out from the wiki.

Fire enemy
Easier than previous Ragnarok
2 overdrive charge meter
Raging overdrive applies strong def buff on boss. Halves damage?
Normal overdrive applies debuff that prevents you from healing for 5 turns.

Just from a quick glance, your water team is better. Elemental advantage and far more utility (debuffs, Mordred, Eidolon with HP, etc). The only good thing about your dark team vs an Advent Ragnarok is Satan.

But then again, I wouldn't know until we actually get the event.