lol, this prufs are so interesting. If you dont know, read this :
Deadly Poison
3 sec cast
Requires Rogue
Requires level 10
Requires One-Handed Melee Weapon
Coats your weapons with a Lethal Poison that lasts for 1 hour. Each strike has a 30% chance of poisoning the enemy for [(25.014% of Attack power) * 4] Nature damage over 12 sec. Subsequent poison applications will instantly deal (12.87% of Attack power) Nature damage.
So it mean that when this rogue hit you with mutilate (double hits in same time) you get damage by deadly poison.
And next thing. About poison damage, assasion rogue can deal big damage with all bursts, so if he use full mastery gems, he rly can do the same damage.