Glass cannon summoner.

[KDSilver]

What "hard dungeon" are you dying in ?
The best way to increase survivability in doing mechanics correctly.

So we could maybe explain some thing, but you'll have to tell us what dungeon.
Dungeons are very forgiving when it comes to mistake. And I doubt you meet healer that never heal you.

OR

You're extremely undergear to the point that you don't even survive unavoidable damages.

EDIT: I checked your lodestone character page and indeed, you need to change your gear.
Try bying some ilvl 270 gear in Idyllshire with your poetics tomestone or buy some to a vendor in Rhaglr's Reach
Change your weapon(book) and rings first. They are the weakest armor you have.