Need help with my sunder build feeling really squishy.

Hi guys,

I need some help with my build. I was following this build "https://www.pathofexile.com/forum/view-thread/1979204" And fought I followed it quite well and got my gear near his. I do have the boots but swapped them out to cap my resistances.

I'm okayish with mobs and my damage isn't the best but it's manageable, but my problem is I'm getting one shot by every tier 8+ map boss and don't no what to add for defencese to make me more tanky as I'm still kinda new to the game.

My build - https://pastebin.com/B0wAaH8X