POB: https://pobb.in/-54cPQorQeEE
After so many tests, this is my best attempt at implementing the Tainted Pact. Although maintaining the leech duration part is solved, I'm still not sure how to scale the max hitpool further. Scaling max life with Petrified Blood seems suboptimal, while ES, Evasion, and Armor are useless because we only care about one-hit damage. So I tried to use Ward instead, but with so much unique gear needed, there are not a lot of options to scale Ward other than boots and a flask. It feels a lot better, but ofcourse, without Olroth's flask, it's not up all the time. I wish there were more sources of Ward scaling in the game. I believe ward will be the solution for this build archetype, and it will be nice to see ward have more uses other than ward-loop builds.

The build is pretty much 90% finished, I don't see any possible upgrades besides more levels, Voices with 1 or 3 passives, and Helmet Enchant. Let me know if you have any questions or suggestions.