TLDR: tanky poison totem build that doesn't require Progenesis or any expensive chase items. 20-35M poison DPS after ramping, ailment immune, stun immune, 30K armour (50 with flasks), 100% spell suppression, good movement speed etc...

Pros: Decent DPS, surprisingly tanky outside of DoTs, Uber viable, decent farmer, fantastic recovery while farming due to poison life on kill, minimal reliance on flasks.

Cons: Poison ramping, totem gameplay annoying for some (not me), DoTs are dangerous, no phasing which makes Sim30 undoable for this build but this is probably fixable with more investment

PoBs:

Current PoB: https://pobb.in/T_7lylvYXzrq

A higher DPS barrage based PoB I was moving towards: https://pobb.in/QAmcForvSX98

Budget: Approximately 12-20 divs for lower DPS version and 15-25 for the higher dps version. It would be possible to do a 10 div challenge version of the build that could kill Ubers with the right person playing it.

Mechanics:

Defense: Fourth Vow + Divine flesh + Juggernaut is pretty well established at this point. You convert some elemental to chaos which increases the effect of unbreakable by reducing ele damage taken and giving more value to armour. You also get to use armour against chaos hits through Fourth Vow which is great. Adding Darkscorn into this allows you to get a large bonus to your physical damage mitigation as 25% of your phys damage taken is converted to chaos which benefits from 100% of your armour still. We get endurance charges through Juggernaut and have good armour. The result is a character that can survive many different big shots including things like ball hits on Uber Searing Exarch.

Things it can reliably tank: Uber Exarch balls (1-2 hits and not running around collecting them), Uber die beams, tentacle attacks from Eater,

Things it can't reliably tank: Shaper Slams, Sirus meteors, Maven memory phase, feel the thrill of the void beams which apparently hit harder than DIE beams.

Ascendancy points: I tried different iterations. They all have some advantages. Use as you like it. I think the armour - > ele reduction one is the only thing I would strongly recommend.

Offense: Scaling poison DPS through things like Ming's Heart and physical damage instead of Covenant and chaos DPS. Otherwise, standard poison totems stuff. You have to get Wither from a Glorious Vanity but we are using that anyway for Xibaqua and Divine Flesh. A lot of synergy with Ming's here as you get a ton of chaos res from it.

Videos:

I took a bunch of footage last night on of my first Uber kills but something was jacked up with my recording device and it all looks terrible. I did Cortex deathless and Exarch/Shaper/Eater/Sirus were all fairly easy with 1-2 deaths. Sim 30 I did pretty shitty on but I think its 90% fixable with reliable phasing.

If people are super interested I might upload the crappy videos but I am not super thrilled with them.

A few notes:

All budgets based on current prices, things are always more expensive at league start. This is not a starter.

Fyregrass put out an "immortal siege ballista pathfinder" earlier this league. This character is probably not as good as that one but doesn't require the same level of chase items.

If Vengeant Cascade gets nerfed you will lose up to 1/2 your DPS. Since I sort of see something like that happening, I am not pursuing this too much further given a new league is coming. If Fourth Vow doesn't change I'll probably instead try to go Champ and Ancestral Protector totems or just something different.

I actually regret going Juggernaut. I think Champion is the right play. Adrenaline is a massive buff and full time fortify probably outperforms most achievable levels of armour for ele damage. See here. https://pobb.in/QVzkuvHMrn0S - champ version.

The other option is actually Raider where you take all the onslaught stuff, frenzy generation and the phasing/suppression node or Pathfinder and take the standard fare plus Quartz Infusion through F/F jewels. As Raider you'd then take flesh and flame to get either Far Shot or Nature's Reprisal, or something. Probably best option offensively, but that wasn't the purpose of this build.

Fourth Vow v. Doppelgangers - I haven't tested it, but I am guessing fairly interchangeable. Fourth Vow has better stats in many ways but benefits from armour. If you were any sort of evasion based ele-chaos conversion character then Doppels would be better probably.

Full DPS is x14 because of two hits from Vengeant Cascade and 7 ballistas. This is theoretical, it varies in combat.