EDIT: Got the build together, I'll put together a showcase tomorrow (its is... quite tanky)

Theorycrafting PoB: https://pastebin.com/AN4uPSab

I've been thinking of making an immortal build to loot fractured fully delirious maps. It is mostly just for fun, to see how cheap it can be to make a character tanky as fuck if you focus on little else.

Requirements are:

Fast (200%+ movement speed)

Tanky (unkillable even in highest level of content)

Because of this, pathfinder is basically mandatory; otherwise, since you can't kill mobs, you will have no way to sustain flasks.

I opted for pathfinder/gladiator. Necro gives more block, but we already have enough without. I also use 'The Traitor' keystone from Balbala brutal restraint, because we only care about 2 flasks (quicksilver + granite/jade). You could use granite and jade, but honestly I think 300k armor is enough.

I've thrown together a PoB and it seems like it will be sufficiently tanky, with 8.8k es, 5.8k (LUL) ES gain on block and capped block chance as well as 250% + movement speed. I think total cost should be at most 10 ex, with most of that being the belt (which is honestly optional but BiS for moving fast).

Does anyone have any advice for improving this build?