As for Typhon Ragnarok, the DMM wiki didn't list the HP amount for the boss, or it's damage range. However based on their contribution, one round of normal Overdrive on a water party was around 4000 damage (with 1 buff of fire elemental resistance), and one normal attack, again with 1 buff of fire elemental resistance, was 2000 on a single member. And they recommend a party that focuses on self buff, rather than boss debuff, because Typhon has a random chance to completely dispel any and all debuffs on her. As far as they know, this dispel triggers in any condition, raging or not. Hence they suggest either Andromeda for the strong heal, or Joan for the self buff.

Personally, I'm going to run Joan with Black Propaganda, Shiva, Poseidon, Aphrodite and Sol, along with Yatagarasu as one of my six eidolons.

As for Garuda Ragnarok, again it is a damage-mitigation strategy as she doesn't have much tricky buff/debuff/overdrives to worry about. I'm again running Joan with Black Propaganda, Summer Sol, Amaterasu, Brynhildr and Agni.