[spoiler]I did it with the following party (all retired at lvl 70 and now back to lvl 70. Maybe I overdid it

)
F: Dark Hunter, Protector, Medic
B: Troubadour, Survivalist
I already defeated all three, and based on my experience with them, I can tell you that the main forte you have in beating and to survive all three is the Troubadour and Medic.
The main key skills you will need to survive are the following:
- Immunize (Medic)
Coupled with Armor like Moss Coat, it will reduce the damage you take by a lot. Always make sure to have it casted.
- Bravery (Troubadour)
As mentioned above, by Wolkenritter, it will prevent you from getting Confused. Boosting the damage you do to the dragon is extra icing on the cake. Always make sure to have it casted.
- Erasure (Troubadour)
When your Troubadour doesn't need to cast Bravery or Relaxing, cast this. It will eliminate the buffs on the dragons, like their Defense buff (reduces all your attack damage to single digits) or their Regen.
Handy skills you would want to have better the odds:
- 1st Turn (Survivalist)
Getting the 1st initiative to use a skill before the dragon helps a lot, especially when you need an emergency Salve II/Cure III for example.
- Gag/Shackles/Cuffs (Dark Hunter)
When you succeed in getting the dragon binded, it will definitely give you some breathing room. And these 3 skills are better than the Hexer's since they still do damage.
- AntiFire/AntiCold/AntiVolt (Protector)
Useful only when you actually nullify their Elemental vs party attack. That is if the dragon decides to use that attack the same turn you use these. Else, you probably be better off Smite-ing.
- Relaxing / Healing (Troubadour)
Regen TP/HP is always good. But with the dragons getting rid of the buffs, this isn't too important. Also, Healing works better when comboed with Stamina, which you probably won't have enough buff slots for.
- Defender (Protector) / Shelter (Troubadour)
Use either one, not both. Comboed with Immunize, you will reduce all damage significantly. But as usual, with the dragons ridding the buffs away, not a priority.
- Salve II (Medic)
Party heal, nothing much to elaborate
As much as Axcela III will help you in getting a boosted Immunize, etc., you might instead not even bother using them since the chances of getting your party buffs eliminated are high. If you're high on cash, go for it I guess. But, not important.
Having items to revive/restore TP/restore HP are more important in my book if the Medic just so happens to get KO'ed.
As for getting their item drops.. well I can't help you much there besides having luck and Scavenge.
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