/castsequence reset=combat/5 Steady Shot, Wrath, Mind Blast, Haunt, Steady Shot, Wrath, Unstable Affliction, Devouring Plague, Wrath, Black Arrow
This is the sequence that I used and it kept up Insect Swarm, Corruption, SW:Pain and Shadow Weaving, Shadow Embrace and HoP with high up time on everything else. Since Steady Shot is not affected by spell haste, you do need to reduce the cast time with ranged attack speed talents like serpent's swiftness or efficency. I recommend efficency.
As much as I like black arrow, I may play around with the devouring epic enchant instead because almost any movement made me drop the juggle.