Spikey One-Shots out of nowhere

I am a returning to PoE after several years. I have been playing my Marauder named Hulk Smaash. Up until recently, I had felt pretty close to immortal. After I completed the game and started doing maps and my third ascendency, I am now starting to get one-shot out of no where. 90% of the time I am fine and encounter no trouble at all. However, just recently, I will fight normally and just up and kill over for some reason and I am struggling to figure out why.

I have 70-83% dr from armor. High end when I am stationary for a few seconds. Maxed res and 2k life. I tried looking it up and what I came up with was:

* My Chaos res is -11. I thought I saw guides that say you don't have to max it. I haven't learned the crafting regiment to put chaos res on my gear yet.

* My evasion is low. I am working my way towards some armor/evasion nodes on the passive board. But the hits are 1-shots so I think this would just prolong it and it would eventually happen anyways.

* My life might be too low? I have just under 2k. I never seemed to think it was a thing since I never had this problem before.

* Crit hits? This made the most sense to me. I respec'ed into the passive that reduces the damage I take from criticals by 30%. But it didn't seem to help. Is the 30% an additive take away or a multiplicitive one?

* Elemental pierce? I am right at the cap for res. Is it possible I am getting my res pierced?

Your defenses are all around quite low, especially considering that the league mechanic produces quite dangerous rares.

1. Your physical damage reduction is lower than you think. Armour works better against smaller hits, and the number in the character panel accounts for a default attack by a white skelly. So your actualy DR against a dangerous attack is probably more like 30%.

2. Negative chaos res is not feasible anymore. So many league mechanics (just like the current one) over the years have introduced mobs which deal chaos damage. Crafting hybrid chaos res on gear and looking for amethyst rings as your ring bases goes quite far.

3. Evasion is quite hard to come by on your side of the tree. If you cant fully commit to it, might be better leave it be completely. That way you can grab Unwavering Stance and Magebane without downside for example.

4. Okay, this is the biggest one. 2k life is *hilariously* low. You should look to *double* that as soon as you can. Take all the life nodes in vicinity. Take the +50 life mastery. Craft life on your rare gear where you can.

5. Yup, crits is another big one! "Reduces extra damage from critical strikes" is additive, but still a good node. Again, this league mechanic is super rippy on that front as well. Crit immunity from Brass Dome would be a possible angle to solve that.

6. Overcapping res does not protect against ele penetration. "Just" capping is fine for now, you usually want to overcap for curse maps.

Other things you could look at to improve your tankiness is using the correct flasks, using 1-2 defensive auras, checking if spell suppression is an option for you, grabbing fortify effect and using a guard skill.

In any case, sharing your build/character would help tremendously in assisting you out more specifically.