Impossible oneshot from Konu, Maker of Wind (invasion boss)

Bug report number: 1 038 679 986.

He oneshotted my character with his "FireShield" ability in T16 Elder Atoll map.

Evidence why this is a bug:
1. According to poedb, "FireShield" ability deals up to 12631 fire damage in T15 map. In T16 it will be no more than 13500 maximum fire damage.
2. Even in case of critical hit it is 13500 * 1.1 = 14850 maximum fire damage (default monster 110% crit multiplier).
3. The only damage map mod is "95% extra fire damage". 14850 * 1.95 = 28958 maximum fire damage.
4. My character is wearing Loreweave with 78% resistances. This reduces fire damage taken to 28958 * 0.22 = 6371 maximum fire damage.
5. My character is using fortify. This reduces damage taken to 6371 * 0.8 = 5288 maximum fire damage. (i had fortify buff on me 100%)
6. My character have 6759 maximum life. 6759 > 5288 which means my character should stay alive after his hit. (my character was on full life 100%)
7. There was no other monsters near (which means no one could give Konu damage aura or amplify incoming damage on my character somehow).

edit:
8. Even if you don't believe me that my character had fortify ON, according to numbers my character should still be alive after hit of "FireShield".

PS: "FireShield" is punishing melee for no reason while provide no threat to ranged playstyle (spells/bow). What is wrong with game designer who developed this ability?