Regarding Ragnarok:
Her Rage bar is extremely weak. I forced her into Rage on the first turn using skills. Her Rage Overdrive hits pretty hard: ~3k x3 damage neutral element with -55% ATK. I never saw her Normal Overdrive. Joan with Black Propaganda seems like it'd work well. I'll continue to use Mordred to make sure my debuffs land as Water element, but I'll bring Jorm friend eidolon next time for further damage reduction. I don't expect to get hit by the Normal Overdrive at all so I won't bother with countermeasures.