Deadly Poison is everything to an assassination rogue. It makes up between 35-40% of our single-target DPS. Our mastery bonus, Potent Poisons, increases our poison damage and causes mastery rating to be our best stat by far. Our primary finisher, Envenom, is designed specifically to increase the amount of Deadly Poison procs we see. Mutilate, Dispatch, and assassination's other abilities are all minor players compared to Deadly Poison.
Deadly Poison is also the key to assassination's AoE performance, as it makes up over 50% of our overall damage. All of our AoE decisions have to be seen through the lens of maximizing Deadly Poison's damage. Fan of Knives is the key to applying Deadly Poison to several targets at once. When there are more than two targets around, we replace Mutilate and Dispatch with Fan of Knives as our main combo point builder and work from there.