Honestly, I couldn't figure it out. I got the Echo after 3 attempts or so (for those who barely survived it after a few tries, that's why) and downed it easily from there with a Second Wind and Bloodbath.

Sort of wish I didn't get Echo and could down it properly My theories would be either:

-Warp just before the cast bar finishes
-Opposite pillar of Noctis as mentioned