Ever since I was talking about how Venom Gyre is probably not viable to kill Uber Bosses, I was kinda hooked to stretch the build to my limits (even more so since my Nimis Caustic Arrow build turned out to be not as broken as I wished for).
Current PoB: https://pastebin.com/e2LSAx4V
The single target damage turned out to be absolutely bonkers at some point and has just evolved ever since until this stage.
A lot of gear is self crafted, a couple of notable expensive Items:
Omniscience (20 div, found it on my first Exarch)
Watcher's Eye Precision AS/Anger Multi (10 div)
Ele Claw (bought base for 19 div, T4 Aisling crafted 20% double damage while focussed)
Enlighten 4 (7 div)
The rest of the items were either self crafted with essences or bought for 1-3 div.
It's hard to estimate the total budget since you can save a ton of money by just spamming essences on fractured bases and if you know what you want, it's not expensive at all (especially while taking essence nodes on atlas tree).
I'm currently farming The Feared with this build and the only Uber I killed so far was Uber Eater.
Others may follow
(Yes, I missed the Rotgut timing on the fight so no Onslaught :()