I died to aztiri, but game thinks I won

I am not on very strong character. But seems exactly at the power scale just right for what devs seem to ballance atziri at. It takes me few minutes to defeat her. Only to be welcomed by "nuke" entire battlefield mechanic and I have no idea if it has some counter. I could not figure it out after fighting her at least for last 3 hours and dozens of times I failed.

My few last attempts I came to a conclusion... ah so you are not supposed to dodge the nuke. You are supposed to go all in. So it's DPS check like with the Molten Lava boss that walks at you and you drown in lava if you don't kill him fast enough.

But this last attempt she became unvulnurelable just at last 5% hp so I was unable to kill her before the nuke goes off... So I don't know if I was too slow or that always happens.

I died... after respawning I don't get another attempt, game thinks I won and wants me to loot medailon, when I returned to the boss room the door clumbled, I was unable to take medallion and therefore no loot... I don't think I want to even try to fight her ever again. It was pure frustration for me entire league.

Before multimple attempts I died to her 3 times on previous character and succeded once. For some reason she didn't go to nuke state that fight because my damage was high enough. Then I died 2 times on my way to atziri from the Royal Access Chambers... One time to a architect I wanted to kill along the way and next time in random room.

This fight is biggest "f* you" I have ever seen...

I guess I give up on Atziri... come back 20h later when I quadruple my damage and kill her so fast she won't even go into her "nuke" state. ... But I am only gessing at this point.