You are making things too complicated. Don't worry about chain shock, harnessed darkness, or anything else. Thrash-less rotation is guaranteed to be able to generate harnessed darkness stacks and chain shock procs at least as fast as any other rotation. Therefore thrash-less is maximum survivability (not taking into account analyzing dark charge procs rates of different rotations). The only question is the dps and threat you are doing. As I have shown thrash is the worst force/damage of any ability. Therefore spending force on thrash instead of something else lowers your dps and survivability.

In case someone is not aware, chain shock has no dependence on the shock that procced it. It's a different spell, with different coefficients, and crits independently of the originating shock. Critting on a shock does not mean that chain shock will crit, and it does not increase the damage of that chain shock.

A simulator is able to analyze rotations - this is a proof that thrash-less rotation is superior. In addition, a simulator can give you a very accurate dps number, so if you want to calculate dps do it with a simulator, not a spreadsheet.