Newbie need idea/guidance for improving BF + BB + EK + Spellslinger Raider

Update 03/05/21

This is the version that i'm working on.

https://pastebin.com/fWMCkHer

* 6k EHP (600HP + 5.5k ES)
* 1.8M DPS

Still getting killed on 1 hit sometimes. Although the damage increased, it isn't still a boss killer ;-; . It could probably get some more DPS/survivability from watcher eye, cluster and rare items but i don't even know how to start this or how expensive it would be.

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First off all, i would like to give the credits to the guys that made and contributed to the build https://www.pathofexile.com/forum/view-thread/2841809/page/1

Context: I love playing as Raider and tried to play the meta build BF+BB but didn't like the gameplay. Tried to make it semit-automatic, saw the approach of the linked build and did some tinkering.

That being said, i would really appreciate if you guys give me some ideas or sugestions about how to take the build to another level.

Pros:
- Cheap
- Fun playstyle
- Nice clear was able to clear T13 maps pretty easy (still trying to explore the map)
- Fast!

Cons:
- Single target is not that good
- Sustain comes only from Atziri's Promise which is a big problem for bosses
- Can get one shotted by bosses (i'm looking at you Baran)

I don't know how to solve these problems. I suspect that the sustain problem might be solved if going low life ES or full ES (but i don't know how to approach the tree for this, i have never done a ES build)

This is the POB for the build(lvl 100, but the char is lvl 90 and can be seen in my profile "JogaFaca"): https://pastebin.com/wkdRehCQ

This is my take on the Low Life ES version, since i have never played one... i don't really know if it's viable.

https://pastebin.com/9MU2k3dd

I believe that there was a improvement on the tankiness aspect (not really sure since it was only theoricrafted). Damage wise there was a increase but i don't know if it's enough for boss.