Poison issues

I have 150% chance to poison, Lycosidae and the mastery "Monster's cannot block you Attacks" allocated on the passive skill tree but my Cobra Lash still does not poison on every hit. I really do not understand why or how this is possible, are the projectiles from the spell not considered an attack? But I see the health of the mobs going down on hit, there just is no poison being applied.

This is in act 6 whilst leveling.

Thanks! Missed the obvious!