Gunbreaker can be one shot after using Superbolide

I just experienced the Superbolide "bug". When you use Superbolide, there is a window to get one shot after HP drops to 1.

Date & Time: 2019.09.29 16:07 PDT
Frequency: Once
World name: Lamia（in dungeon）
Character name: Zetsukaze Kumotsuki
Monster name: Vassago/ Allagan Balloon
Class/Level: 73(Sync to 50)
Party or solo: 24 men Alliance
In-game time: 12:59 ET
Area and coordinates: The Labyrinth of the Ancients

I used Superbolide at 8672 HP(almost full-health)
Group B Allagan Balloon blew up at the same time when my HP deduced to 1.
Then I was killed instantly.


And here's my streaming screenshot

https://img2.finalfantasyxiv.com/acc...a9bb7bdef9.jpg

https://img2.finalfantasyxiv.com/acc...720db9c692.jpg

https://img2.finalfantasyxiv.com/acc...c29a88b4ec.jpg