Okay, time for a bit of math. Both Hemo and SS are normalized, which means that weapon speed is a much smaller concern for Hemo now (more of a concern than it is with SS due to an additional 25% weapon damage applied, but not to the degree you'd see with it being unnormalized).
Assuming that 100% of the Hemo debuff is consumed, let's see where the SS/Hemo breakpoint is to the best of my ability. Sinister Strike is credited with Lethality (crit = crit * 1.3 = newcrit for modeling purposes), Aggression (6%) and Suprise Attacks (10%). Hemo is credited with Dirty Deeds (120% damage 35% of the time assuming normal distribution patterns, or an average of 7% increased damage) and Serrated Blades (560 ArPen, or ~4.5% Damage in typical raid situations). Weapons are assumed to be the Blade of Infamy/Savagery combo.
SS: ((100.3 * 2.6 + AP * 2.4 + 98) * 1.06 * 1.1) * 1.39
Hemo: ((100.3 * 2.6 + AP * 2.4) * 1.25 * 1.07 * 1.045) * 1.3 + 360
Head asplode. Simplifying...
(260.78 + AP * 2.4 + 98) * 1.621
422.72 + AP * 3.89 + 158.86
581.58 + AP * 3.89
(260.78 + AP * 2.4) * 1.817 + 360
473.837 + AP * 4.36 + 360
833.837 + AP * 4.36
581.58 + AP * 3.89 = 833.84 + AP * 4.36
Uh. Okay. That's not quite what I was expecting... with these weapons, you'd need to have a _negative_ AP score for Sinister Strike to win. Without ANY AP, the 'breakpoint' for parity would be at... hm... 62 DPS. So, if you're using outdaed blue weapons (or greens) at 70 there might be a point at which they'd be the same, but otherwise... no.
Okay then. That was unexpected. Time to do the math again without factoring in the damage bonus then. Cheating and taking some of the final results...
SS: 581.58 + AP * 3.89
Hemo: 473.837 + AP * 4.36
107.74 = AP * .47
229.23 = AP
Also... unexpected, but not as hideously so. Without counting the debuff at _all_, Sinister Strike outdamages Hemo... when you have 229 AP. The factors I did _not_ consider are Adrenaline Rush and Combat Potency, but over a long fight the lower base Hemo cost compensates for this using my Guesstimath, which is of course always accurate.* (* Or not, but someone else gets to do _that_ math).
Interesting. Very... interesting.