Hum, like I stated before, SS usage will break even at 230+ avg potency/sec, possibly lower depending on how much base crit you have.

Looking back at my old sims, it seems most DoW classes peak out around 201-220 potency/sec (including AA), which means that if SS is available to Machinist, then it will be worthwhile to use in your rotation, barring any timing issues (like buff timers etc). It will definitely be useful prior to cooldown usage and any burst period, but very likely not worthwhile during the cooldown period.

Of course, iirc most DoW classes are getting significant buffs/stance changes that will increase their avg potency/sec, to the point where SS may no longer be useful.

Oh well though, because if it is, it would mark the first time that a cross class ability becomes a core rotational ability.