On live, we all know and love Shadow's amazing t13 burst, which spikes well into the 70k DPS region. Sadly, next week it will be gone.
The next closest thing: Mindbender + 4pc t13 + Devouring Plague spam.
Mindbender melees once every 1.25sec, dealing (318 + 0.58 * SP) [experimentally obtained value - subject to some error) shadow/melee damage.
Cast DP every 1 GCD or 1.25 sec, whichever is more.
12 DPs total (assuming at least 10% haste).
Total time spent soft haste caps at 20% haste, at which point you're limited to the swing speed of the Mindbender. (Time spent: 15sec + 1GCD)
The DoT continues to scale with haste beyond that, but it's a small effect.
Devouring Plague deals (3336 + 2.3 * SP) on cast, and (328.8 + .156 * SP) every 1 sec, modified by haste.
This comes out to 12 Mindbender melees for 97k, 12 Devouring Plague casts for 440k, and ~33.8 (24 w/o mastery) Devouring Plague ticks for 88k.
38.6k DpET over the 16.18 sec activation.
As you can see, the DpET is lower than most of our standard rotation, and should only replace Mind Flay and Mind Blast within the same window. With this in mind, the damage gain from the whole thing is much more subdued. Assuming one VT cast, one SW:P cast, and two SW casts within the window, we drop to 8 DP casts, dealing a mere 277.3k more than the Mind Flays it displaces. In total, this deals 636k over 16sec (731k with Twist of Faith), leaving Shadow no longer viable for 30%-nerfed H Spine of Deathwing. It can only barely scape "just pulling your weight" in the best available gear, including a legendary staff that takes months to farm up.
Note that, while other combinations of talents can produce higher burst on one individual tendon, they cannot reach as high of an average performance across all 5-6 tendons. Power Infusion is only up for half of them, and FD;CL relies on having bloods DoT-ed up beforehand, and - crucially - them not dying. Insanity and Divine Insight are simply bad.
---------- Post added 2012-08-23 at 03:08 AM ----------
Although I suppose we could be taken as a healer. Alternating VT for mana and actual heals throughout the fight may allow a raid to run one fewer "real" healers. With Blood Corruption: Death mutating after the first dispel, Mass Dispel is now a good option for dealing with the multiple dispels during a roll and at the start of the fight.