Too Many OneShoot from Outa Space !

I have a Tank Build very very tanky , but sometime a trash mob insta kill ? WHY ?
I can tAnk Omniphobia in T16 map irradied and die face too a trash mob ?
I think something wrong.

Please GGG make ur game more fair make something about OS , 90% armor ,78 all res 51 chaos res (armor applie to elem damage) and ramdomly a trash mob OS me !

I think its the mob scaling.
When the physical mob jumps at you, the damage is insane if it connects.
However, Omniphobia also just ignore shields.
Maybe the big slam is a red flash move but you dont see the indicator.
It hits really hard and difficult to deal with in the middle of a swarm.