Am tank so I'm used to keeping an eye on the field with a lot of crazy camera twirling. Figured out after a few uses of the duty action that it was an AoE and that it had no cast time. Promptly ran back and forth spamming it where the orb paths intersected for best efficiency. You can calculate trajectory based on the lines they leave behind. As she releases more orbs, they will get closer and closer (to make you feel genuinely panicked, haha). Arenvald pulls his weight pretty well so you really only have to actively worry about your side (I kept an eye on him anyway, never trust NPCs who are stated to be noobs in game). I did not worry about DPS once I realized the point was to save the other NPCs. If you try to DPS during that portion, you will fail. I am used to using my arrow keys in other games to navigate so had no problem switching around.

I did not use sprint and the orbs got very close, but cleared it on the first try and watched all the unbelievably cool stuff go down. Fun times!