Uses lots of non physical damage abilitys to avoid armor at all cost. Primal death is your primary, Blazing strike finisher. Keep puncture up. Backstab every CD. Scourge of darkness every cooldown. Keep expose weakness up. Keep Baneful Touch up(use malice as soon as you get it up the first time, for maximum uptime) Dusk strike every cooldown. Even though you have Lingering Flame, you may have to occasionally throw one fiery spike in your rotation to keep it up. This spec is designed to have the most modifiers to poisons. Virulent/Lethal is what is being used here. However, you can drop Fire and death attunement(3% damage) for 1 point in melted skin (5% damage) and 2 points in advanced flanking(6% crit on backstab)however, the poison modifiers don't effect hellfire, so you would replace virulent(10% more proc rate, 15% damage increase to it, and hellfire is unaffected by poison malice.) The spec had 4 points left over, and decided 13% attack power (riftstalker) would be most ideal.
Overall difference of hellfire and virulent: 6%crit backstab + 2% damage, vs poison modifers for virulent.