PoE IL_Giudice, Cold builds

I'm following TriPolarBear Cold Dot Elementalist build, i'm clearing quite fast (i guess) even t16 maps. Problem is that sometimes i just got oneshotted and i don't know why, even in T12/14, so i keep losing xp and it's been more than a week now and i'm still at 93. Am i missing something crucial? Thanks for help!