I think i know what you're talking about with poison builds. The mamushi snake robes are definitely your best friend here, since they create those poison clouds whenever you check bodies. Pretty much everything revolves around getting poison to trigger as much as possible, so grab the violet night katana for deflect triggers and the stone heart kusarigama to spread it around.

For the actual gameplay part, you'll want to stay mobile and strike quick. The key is getting those vulnerability procs going, which you can do by vaulting enemies with the mamushi hood, then hitting them with poison attacks. Stack the bone of the fallen warrior trinket with this setup, and you'll get poison triggering off posture breaks too.

Something interesting about the affliction effectiveness mastery skill is it gives you a solid 12% damage boost, which really adds up when combined with cyclone blast for spreading poison to groups. The whole idea is to hit fast, get that poison going, and then back off while it does the work. Those poison clouds from investigated bodies are super helpful for controlling areas, especially if you combine them with smoke bombs to keep enemies bunched up.

Just keep in mind that your best damage windows come right after making enemies vulnerable, so time those vaults and deflects carefully. Once you get the rhythm down of applying poison and creating space, you'll find yourself taking down entire groups without much risk.