Help with Venom Gyre Deadeye Build

Hey,
I need help with my Venom Gyre build. My DPS on bosses is very weak and I die often. I know I have issues with chaos resistance, but I don't know how to fix it yet.

I tried playing with a shield today, but it seems like nothing changed except my DPS is down.

Also, is there any way to fix the mana issue? I'm running low on mana and have to run without flesh and stone.

https://pobb.in/6sXdReFvMI66

Any tips on improving the DPS and defense of this build?

First of all: are you sure your elemental resistances are ALWAYS capped (even without flasks, because you don't have a reliable source of flask charges on bosses)? Deaths on bosses might be caused by having not enough resistances.

Mana problem can be fixed by taking additional reservation efficiency. As you're using massive ring thread of hope, you can allocate 8% mana reservation passive (between scion and shadow starting points). By the way, why do you need to automate tempest shield? It won't really work, because tempest shield is a reservation skill.

I don't have ideas about damage, since I haven't played this kind of builds. I guess, you just have to get more dexterity and other build-enabling items.