Food: Dubious Camoran Throne
Pots: Tri-stat.

Optional: Vampire Stage 3 to mitagate some damage (not really worth it).

FRONTBAR: 2 daggers
Crystal Fragments: Only use this when the buff is on (icon shows the skill in red color).
Deadly Cloak: For damage mitigation and AOE. Cast every 20 seconds.
Shrouded Daggers: MAIN SPAMMABLE.
Volatile Familiar: Activate your pet in this bar, not in backbar.
Tormentor: Activate your pet in this bar, not in backbar. Drop this skill once target is below 50%.
ULTI: Greater Storm Atro: MORE DAMAGE!!! Also, gain 2% more damage for each Sorc skill slotted.

BACKBAR: Bow
Daedric Prey: Make all your pets make more damage.
Hurricane: Gain resistance, speed and AOE.
Arrow Barrage: This will proc the weapon damage enchant. (light attacks work too).
Volatile Familiar: DON'T activate your pet in this bar, do it in frontbar.
Tormentor: DON'T activate your pet in this bar, do it in frontbar. Drop this skill once target is below 50%.
ULTI: Power Overload: Just for the 2% damage buff pasive, don't use this.

ROTATION:
Prebuff: Deadly Cloak and Hurricane
Arrow Barrage on target (be sure in "Gameplay" that you have set your AOE in automatic)
Deadric Prey on target
SWAP BAR TO FRONT
Activate both pets
SPAM Shrouded Daggers and occasionally use Crystal Fragments when the buff is on (skill in red)
Refresh your skills as they go off.

About your Ultimate, be 100% sure Deadric Prey is on target during the whole lenght of the Atronach spawn. You will lose a lot of damage if that skill is not on.

IN CONTENT: Just drop Crystal Fragments and add some healing skill. Dark Deal is a good option because it will give you more stam back, but if you think that cast time of 1sec is too much, just replace that with Resolving Vigor from the Alliance Skill tree.