Poison damage on a weapon is the same as any other element (cold is the exception) on a weapon, its just damage. There is no special effect, it does not have a bigger boost to certain skills/spells.
The proc effect you mentioned, vo1os, is totally different. Poison just says straight up +100-150 damage, and that is all it is.
Skill use the total weapon damage to calculate their damage (so if poison darts so 120% weapon damage, its 120% weapon damage no matter what elemental affixes you have, poison won't give it a boost).
Cold is the only small exception, cold damage weapons have a chance to slow enemies. To compensate for this, cold damage appears in smaller amounts (so an item could roll +100-150 poison/fire/etc, but a cold roll on the same item for the same budget would be lesser, say 75-125 (made up number)).