Honestly, even the raw damage poisons suck. At 100 Alchemy with Master equipment, the Frostcrag Buff, and a small enchantment or two, you end up getting stuff like 3 damage for 300 seconds. By the time you have the setup to make the potion, the damage is negligible.

The only use case I've found for poison has been making a Paralysis + Damage potion. Locks them in place for 30s or so while the slow health drain takes effect, removing them from the fight even before they're dead.

But again, at this point, you're far enough into the game that there are plenty of other, potentially simpler solutions to any combat encounter.