I don't think he is pulling, Ryu-Oh is good but he is waiting for both Cthulhu and Magic Release Nike.

Anyway the Ragnarok is fairly easy. With Poseidon (or Jorm), Mordred & Sol, boss never reached higher than 800 damage on its overdrive, raging or not. However, the raging overdrive DEF up buff was rather stubborn. This made the the rage bar quite hard to deplete. Still, Sol and Nike's heal were all very useful and my whole party never dropped below half-health. I did intentionally let the boss have a non-rage overdrive on my party just to test out the effect. Nothing too spectacular if you have a way to dispel (I had Poseidon). I would say the biggest take away is to use the time when the boss has no DEF up really efficiently. I timed my full burst with that and the boss's health dropped by 1/3 or so.