Need Help with my Volcanic Fissure of Snaking

Hi,
I kindly ask for your help with this character.
It's good with mobs, some times having a hard time with rare mobs at t15.
The real problem is with map bosses and mercs. I literally get 1 hit by mercs even with 5 endurance charges. With bosses, it's really weak, takes a lot of hits. It's kinda squishy too. I plan to go crit if I get enough currency, though I'm not sure what I'm doing incorrectly, I might waste my time going crit.
Thank you very much.
https://pobb.in/wzqPaINHX5dl

you need to be prioitizing armour as a lower left build

your helm, gloves, boots, all have 100 or 300 armour

get the lvl 84 base in every slot

https://www.poewiki.net/wiki/Guide:Best_in_slot_base_types

your eldritch implicits on helm and chest need to be phys taken as element

you are dying because you have no mitigation except armour and max res, and your gear has no armour and your max res isnt being used for anything but elemental damage (phys is the big culprit of deaths in poe1)

you are using triple life flask: get granite flask rolled with % armour during effect

do your 4th lab and grab defy pain if you want more defense, or aspect if you want more dmg

you are not at the point where crit is the answer. get more lvls, better weapons/links/awakened gems, and keep using RT