I just can't get the HP to survive a same round double strike. It almost makes me want to go with a Neptune / Meteor leader setup for the Fire resist, but that's such a huge waste of a leader spot for just that one round. Not sure how it'd work on Master. But not having my own Golem / Shiva to knock down the Dragon defense seems to limit my options.
Right now I'm running a Neptune, Water Mech Warrior Midgard, Crystal Aurora, Rainbow Keeper, and Graviton Earth. That puts me at 11,332 HP and last time I took a friend Neptune along since none of the Shiva's were up. Thinking about replacing the GVE with a Siren or Echidna / Viper, but still no way for me to do 570k HP in 4 Turns.
Oh well, this is all just theorycraft at this point since I likely won't rerun it until it goes 2x. Need to farm Green Kings for my ADKs, Ceres, Artemis, Highlander, etc...