Addendum:
After having done the laundry, I gave it another go. It succeeded, took 30 minutes.
- I completely disregarded any mechanics, just held the "+" button down all the time. When I died Aurene ressed me or I continued from a checkpoint and ran back to the boss.
- I gave it a lot of time for aurene to tell me to wreck the crystals after each storm (that's it perhaps?)
I now realise that previously the Kralkatorrik was stuck with the beak in the ground so I could not get onto the third strom phase. This is what made me think I was too quick to destroy those crystals before Aurene has told me to.
Hope this helps someone.