What am i even playing

Can anyone explain without coping why is my 90% all res cf getting LITERALLY one tapped by every single merc? it doesn't matter what gear they have, at first i thought it was my bad, that i was undergeared, but now that i'm fully juiced it's still happening! been fighting mercs and evading 99.9% of their projectiles just in case but then boom, frostblink one tap..
Why is this a thing and why wasn't it hotfixed yet? do they have some hidden "deal 500% more damage" mod or something?