, 11:15 AM
IMO the rotation/priority approach to this analysis is better done by simulation - SimulationCraft would do a better job of taking care of procs and irregular rotations. I use a different approach which was valid until the 1.5 patch and may still be valid but I no longer have 100% confidence in it:
Note: I used this method because I did not have time to program SimulationCraft (no support for darkness) and this was a quick and easy way to analyze the thrash-less rotation.
The assumption is that assassins are force starved. Before 1.5 this was true except if wither was used every 15 seconds and you were regularly gaining bonus force from defending/shielding. Personally I believe that any extra force should be used for more wither attacks as a priority. In 1.5 the additional force from defending/shielding make it possible to use wither every cooldown and still be in danger of force capping.
Once you realize that every point of force is precious, dps and tps become irrelevant. Instead maximizing damage per force (dpf) and threat per force (tpf) become the goal. The question is whether thrash has a role to play in the rotation. Every time you thrash you spend 23 force, but you also spend 1 gcd that could have been used for something else. The only ability you can always use is saber strike, so the question now becomes: what benefit does thrash have over saber strike?
Benefits of using thrash instead of saber strike
1. The additional damage that thrash does over saber strike
2. The additional damage that an energized shock has over a regular shock multiplied by the chance to proc energize
Costs of using thrash instead of saber strike
1. 23 force
Using my gear the average damage after mitigation (~30% with armor debuff) of:
1. saber strike = 542
2. thrash = 1018
3. shock = 1319
4. energized shock = 1796
Which means that thrash generates (1018 - 542) + (1796 - 1319)*0.5 = 714.5 extra damage at a cost of 23 force. This means thrash is around 714.5/23 = 31.1 damage/force. Every other ability has a higher damage/force. So in the end, even if you have extra force to spend, it is better to save it for other abilities *except* when you would be force capped.
In the end the rotation in 1.5 is mostly the same (thrash-less) except occasionally you may have enough force to thrash and hope for an energized proc. Fishing for a proc is highly unadvisable. Using thrash over shock or wither is also highly unadvisable. Mentally prepare yourself to use thrash on fights will many melee/ranged attacks, otherwise ignore it (10.4 force/s is not enough for the basics).
Note 1: I used 0.5 for the energize proc chance. I have not seen a conclusive analysis of boss defense or even whether defense is consistent across all bosses. If you would like to use a different number please go ahead.
Note 2: I don't use tool-tips to calculate damage. I use average weapon damage, average coefficients, and factor in crit chance, accuracy and surge, but excluding temporary buffs such as recklessness.
Edit: Fixed some numbers.