Knights of Cygnus Skill Tables

Poison Sling stacks with venom to create an extremely powerful poison. It's only drawback is overkill - there aren't any monsters below the 120 range that having so much poison stacked would be useful.

I think you're misunderstanding how much damage Poison Sling and Venom do.

You learn Venom at 110. By then, you shouldn't be using Poison Sling to train. It only has one active chance to inflict Venom. You should probably be able to do the same amount of damage, if not more, in a single Triple Throw, as well as having a chance of inflicting 3x Venom.