how to stop getting one shotted?

as you might see from my char name, i get one shotted alot lol. but this league i got real lucky an managed to get alot of div together and get my lac glad fully decked out, followed a build exact and even managed to get HH ( i swap it with inspire learning sometimes and use other belt tho

but i still get one shotted by stuff like the RF in uber atziri, etc and randomly in maps. IS THIS NORMAL? or am i just awful at the game. this is BY FAR my best char ever and it doesnt feel that much tankier lol, even though im also lvl 90 which is my highest lvl yet

i think ppl can see my char for league on here? if not how can i link the info to get some feedback, TIA. i really enjoy the game but every league find my self frustrated at how often i get one shot and have no idea what killed me, really bringing down the enjoyment when my character is getting one shotted even by the current league mechanic at 50% difficulty in a lvl 78 zone when im 90 lol. i keep coming back to play a league hoping it will be better , and i was so confidient this league due to actually gettnig a solid geared character but like i said... still happens :(

with the amount of times ive died getting to level 80 to 90, id probably be 93 or 94 lol if i died even 10% as much

just for adding a bit more, off the top of my head these are some things that one shot me 50% OR MORE times when i encounter

-maven/eater/exarch/atziri etc
-anytime a breach boss spawn in breach
-breach boss in Breachstones
-crucible league mechanic when above 40%
-atleast one of the spawns in a harvest

still get slapped by other stuff like heist/abyss occasionally but not NEAR as much.

i feel like good gear at lvl 90 should be able to atleast have time to react to stuff like this? or am i wrong?

Your character tab is still private so we can't see.

How much life? What are you using as defences?

Most of the stuff you listed are bosses. Bosses in POE use telegraphed attacks you are supposed to dodge manually, if you fail to do so it's usually a one shot for regular builds. The attacks are meant to kill you if you fail to dodge them.
Havest spawns also have telegraphed attacks that can hit really hard like the big bears with their stomp attack.

So yeah getting oneshot by that kind of stuff is normal. It's possible to make builds that just laugh about it all but that requires you to build for it. You won't accomplish it with regular capped res 20k armor and 5k life. You need to go quite far beyond that and i'd wager you are probably below that. Most guides these days claim they are tanky but it's usually on a level where they can barely survive a hit during maps, not face tanking bosses.

I happen to be playing a Lacerate character this league for fun who is super tanky. From playing melee characters (though this one doesn't feel like melee), I found that to be super tanky, you need more than just good HP and armour. You need a busted amount of recovery of some form.

My character has some decent gear (nothing hard to afford) but what makes him near unkillable in most situations is the fact that he leeches for over 3300 life per second while only having just over 4000 life unreserved. So anything that doesn't straight up kill him instantly won't kill him.

Have a look if it helps you with ideas (note he's only L92 because I played him very little as he's my last fun character of the league):

https://pobb.in/YSrmkw1rn_jy

not going to quote all 3 as it will make a long reply, but big thanks to everyone who posted, i will take the advice into account and make some changes on my character and playstyle

thanks!!!