Truth is, oneshots rarely happen after you get past level 12, even on the squishiest characters, unless you have anything that reduces your max hp or increases your damage taken, you can even survive TWO hits if:
>fill one or two slots with the most suitable damage negation bonuses, can be the lowest tier piece of shit item, it will work
e.g. if you're a caster
>damage negation when casting+when taking damage
or if you're meleeing with a fast weapon
>damage negation with sucessive hits+when taking damage
Shit can vary depending on what talismans you got/your character, but there's really no excuse to die so often when there's shit like this in the game, at least try getting a single damage negation at full hp.
"But, anon, I never find any of that stuff in my games??" Nigga, if your team is fast as fuck and only going for boss kills that may be the issue, think about all the chests you are leaving behind, even bodies have nice items in them sometimes, let them speedrun and stay behind interacting with everything until you get a defensive roll.
Just do it bro... please I beg you