Surviability help

As the title says, just looking for someone to check my PoB and check why I'm dying to bosses easily. Clearing is fine and fast but when I get to bosses in when issues arise. It's very hard for me to consistently stay alive during boss encounters, some are a breeze and others I just get hit once and boom dead. I feel like there's no room for it being user error either, I'm just squishy against certain types of bosses. Thanks for any help, here's my PoB. https://pastebin.com/ZZyxSRZS