Delirium monster damage got supicious

I was duo farming with my friend for weeks at both simulacrum and mapping 60% delirious map.
But just seconds ago we both get 1 shot by normal/magic monster.
About my stats:
6200 es without grim feast(12k with grim feast)
1800 hp
42% phys reduction
18% evasion
25% block
77 all ele rest
75 chaos res
that won't justify any 1 shot from normal/magic
Please take a look. Thank you.
P/s: This happen after my friend got crash by a weird bug: Can't not send packet something something