Video: https://clipchamp.com/watch/LuhnZO5rbMB - (includes T16 mapping, and most of a feared rotation that I remembered to record. Caveat: not a video editor by trade)
This is one of the stronger medium-juice mapping as well as boss farming builds I've personally put together, and the upgrading path was smooth and fun so I thought I'd share it. I always enjoy seeing other 'well known' builds showcased so I don't just imagine them while browsing poe.ninja.
tldr it's not rocket science and uses a fairly well established combo: Badge/Ralakesh/Malachai's Loop/Void battery and power charge stacking. EK fires when you stop, so you gain charges, cast, and move (lose charges). Ralakesh's doesn't make the awful charge noise anymore, so this is basically OP now.
It's done 50+ uber bosses (Exarch and Eater in under 5 seconds, see video), a few dozen Feared rotations with 100%+ quant, and all 40/40 challenges solo. I have really underestimated both freeze and killing things as a defensive layer, and while this does use cast on death portal, it matches the spirit of u/Palsteron's recent video. It's so much better at mapping than I expected!
I started this build around day 10 with Aer0's EK map blaster (after self chill explosive trapper didn't pan out for me), and kept dropping defense and adding damage as I never needed more defensive layers other than a portal or two.
It can run all map mods and is ailment immune. (recovery on kill for no regen, ring swap if you want to run ele reflect). For uber bosses, avoid ailments / chance to suppress can be slower but still 100% doable. Maven and Sirus are more about player skill with this than quicker bosses with fewer phases but can be farmed handily.
Comprehensive PoB: https://pobb.in/xeBR6muCY7Cx
My PoE.ninja profile
The PoB contains both a Level 92 ~4div budget setup with 13m damage, as well as a level 100 ~150div setup with ~380m damage. (I actually don't know my costs). I didn't level with anything close to this build and don't think it's easy, strong, fast, or advisable to try.
It has notes I've put in on tricky bits, playstyle, potential upgrade ideas from the base tree, and light crafting ideas.
Let me know if you have any questions!