On a one-minute single-boss fight the build is 31/18/2. It goes deep into Assassination for 
Mutilate, 
Seal Fate and 
Relentless Strikes, and far enough into Combat to reach 
Flawless Execution and 
Dual Wield Specialization.
On one-minute fights two points also go to 
Opportunity, at the top of Subtlety.
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0/100530310321421051-302303202012-002The search runs separately for every fight and faction, and the results only move points that measure close to nothing. What follows applies to all of them.
Why these talents
Mutilate is the spec. For 60 Energy it strikes with both daggers for 75 % weapon damage plus 50 each, and awards two combo points. It hits 20 % harder while Deadly Poison is on the boss, which is almost always. The talent is worth 60.1 % of your damage, because without it nothing builds the points that Slice and Dice and Eviscerate spend.
Relentless Strikes gives each finisher a 20 % chance per combo point to refund 25 Energy, so a 5-point Eviscerate always pays it back. It is the most valuable talent after Mutilate, worth 8.9 %, because Energy is what limits how often you can press Mutilate.
Seal Fate adds a combo point when a Mutilate crits. Each hand rolls its own crit, but the bonus point comes once per Mutilate however many hands crit. 
Puncturing Wounds adds 15 % crit to Mutilate on top of your sheet. Seal Fate measures 5.8 %, Puncturing Wounds 3.1 %.
Malice is 5 % crit for attacks and, in Forever, poisons too. It is worth 4.2 %, and each point also raises the odds of Seal Fate's third combo point.
Ruthlessness and 
Improved Slice and Dice keep the loop turning. A finisher has a 60 % chance to leave a point behind, and Slice and Dice lasts 45 % longer. Removing them costs 3.7 % and 2.8 %.
Flawless Execution takes Eviscerate from 35 Energy to 25, and 
Improved Eviscerate adds 20 % to its damage. Losing them costs 4.7 % and 3.7 %. They are the reason for the Combat points.
Cold Blood gives 100 % crit to your next Eviscerate or Mutilate. In the beta, Mutilate takes the crit without using the buff up, so every Mutilate after it crits with both hands until the next Eviscerate spends it. It is worth 2.8 % here and 2.8 % on a one-minute single-boss fight, where its single use is a bigger share of the fight.
Flexible points
Several points in the build measure nothing on a boss. Here is where they sit and what else they could do.
- The Combat path. Combat's fourth row needs 15 points, and only nine above it add damage. The other six go to
Lightning Reflexes, 
Improved Sinister Strike, 
Endurance or 
Improved Sprint, which add dodge or improve spells you don't cast. Each measures 0 %. 
Venom. The 31-point talent is a finisher that adds 30 % poison damage, but the simulated rotation never casts it, so it measures 0 %. A finisher's combo points do more on Eviscerate. Its point is free. A fifth point of Dual Wield Specialization is the likely better home, since each of its points is worth about 5.7 DPS, but the sim hasn't run that build.
Murder. The benchmark boss is a dragonkin, and Forever's Murder only works on humanoids and giants. Against one of those it adds 4 % damage for two points, which the sim hasn't measured.
What each talent is worth
Every row is a separate run of the build with that talent's points taken out, on the same simulated fights. Because each run removes one talent, the rows don't sum to your damage. The last-point column is the cost of giving back a single point, the figure to compare when you move a spare one.
On every fight
The one-minute builds take 
Vigor 2/2 for 10 more maximum Energy and Opportunity 2/2 for 10 % more Mutilate damage. They pay with two points of Dual Wield Specialization and one each from the poison talents. A full bar at the pull counts for more when the fight is short. On a one-minute single-boss fight Vigor is worth 1.2 % and Opportunity 1.6 %. The three-minute three-boss build moves a point from Improved Poisons to Vile Poisons. Below, every fight's build sits next to this fight's.