How to improve my build?

to be fair, 3k Mana is just not a lot, considering you even have eldrich battery.

me dying from time to time with a hitpool of 1.6k life, 6k ES and 2k mana... I would be surpised if you would not bite the dust regurarely.

I have huge doubts that a 111% magic adorned is worth running with normal sapphires.

You are probably clearing clearing content as easily as it clears you lol

You've gotta get defenses from somewhere! If you're not going to get it on your gear, you've gotta get it from the tree/jewels. If you don't get it from either, you're just building a glass cannon.

I could almost count the investment into defensive stats and affixes from your gear AND tree on less than one hand!

I think you're gonna have to sacrifice some of that DPS or reconfigure something. It's okay though are already doing overkill DPS.

First order of business I think would be to get more mana/ES with a very high ES chest.

There's also a unique amulet called stone of lazhwar that grants up to 25% block chance while holding a focus along with mana/cast speed. You'd need to double corrupt it for +1 and +1 again to approach the juiciness of your current ammy but the amulet is dirt cheap. You can also slap on some very cheap anoints for huge increased block chance and rolling increased block chance on jewels works with it too, which would be enhanced by your adorned. You'd probably hit +1 and +1 again on a double corrupt for a lot less than 2 mirrors but don't quote me on it. Either way, very very accessible defensive avenue for you. If you need the spirit you can get it on a chest and still have decent ES.

I'd also recommend adverse growth notable along with some more increased energy shield notables from the tree or your jewels. You need to get more investment into increased ES from somewhere. The opportunity cost for using adorned-enhanced jewels is the points pathing to the jewels - the benefit is that you can customize the affixes to suit a build (ie. there aren't notables that will grant you 30% increased energy shield AND 40% increased spell crit bonus on the same notable, along with resistances or attributes - that's why it works well for builds that use a lot of uniques that lack defensive stats). Aim for an absolute minimum of 5k mana. I don't even feel comfortable on more conventional MoM+EB characters without 6k+ mana just for regular mapping in hcssf. Mana on kill is also pretty good if you are farming temple/mapping.

Also - if you go the block route, taking the 4 points to Steadfast Resolve will solve your stun issues. It's even a good annoint if you don't have block.