KBoC guy: did another round of regearing after I picked up the super expensive jewels (ff/ff and escape). Gloves, body armour, boots, rare jewel all got redone. Then a million little things had to happen to fix my attributes and resistances after that. For example I had to sell my HH and rebuy a higher roll to make it all fit.
However, the guy got significantly stronger even after I thought there was nowhere to go with it. It doesn't come through very sharply in the POB because the DPS stayed roughly the same. But for instance, I was able to drop Tempest Shield, so I have a lot more unreserved mana. That means that I run out of mana less often, my Laviagna's lasts significantly longer before filling up the bar, and I am rarely OOM when I get hit now. Making attribute room with all T1 suffixes meant I can afford a single chaos res craft so I am always overcapped on chaos res without Atziri flask. I can and probably will switch that into a Wine of the Prophet (just to experience that). Taste of Hate can become Dying Sun.
https://maxroll.gg/poe/pob/ebs480y7
Keep in mind that it says 97m DPS, but it's configured conservatively. In reality I think I get way more than 4 hits per attack under most scenarios where it matters. I am just keeping it at 4 so I can apples-apples compare with all other versions of the build I've played with. Also it's at 16k mana spent recently, but in reality I think I'm capping out my mana sustain at around 20k mana spent recently. This is possible to deduce because I can look at the tooltip cost of KBoC and see that it oscillate around 1.2k mana cost when I am in a sustained fight, and 20k mana spent recently puts me at a 1.22k mana cost tooltip.
Anyway, last league I played multiple builds, and I played for like 6 weeks. I never got to the point where T17s bosses were on farm. They are very much on farm right now. I can do T17 100% deli Abom with pretty much any map mods, and always complete the boss. Some of the tankier mods, like reduced extra damage from critical strikes, 150% more life or more ES, and 80% chance to block attack damage, are things I avoid out of preference, not out of need. It's risk viable, that's all I'm saying, there are no hard bricks.