While I completely agree as to how SsS failed compared to the wonderful likes of Star Diver*, especially, I don't think it even needs special circumstances or like. It just needs decent potency.
With, say, a 20% Crit Chance (2855 Crit), our average PPGCD at speeds capable of sustaining Twin Snakes until just short of Twin Snakes itself via a typical Double-True rotation (which then means clipping a tick of Demolish per Demolish), is roughly 6260 effective weaponskill-potency over 18 GCDs, or roughly 348 weaponskill effective ppgcd (prior to GL, since that'd be constant anyways).
For SsS to run equal that with that, it'd need 561.5 potency (which is twice the above effective eppgcd minus the value of the chance of generating a 5th of a TFC, divided by the Twin Snakes multiplier and base Crit effective damage multiplier [crit-chance times crit-damage multiplier]).
If we didn't want it to be used constantly, but did want it to see use for rotational sync and multiplicative burst, we'd just set it to, say, 540 potency, a positional short of standard rotation as if to compensate for the fact that it has no positional and can be used at any time. And I could have sworn that was much nearer the originally advertised potency than what we ended up with, too...
Much like TK, SsS's failure seems a case of the devs not trusting players to be able to do the math and thus squishing a skill down entirely to niche use through potency adjustments, such that all but one of its originally intended uses are obviously disallowed, rather than trying to provide sufficient in-game tools to deal with the game's complexity. That, more than anything, seems to be what really holds Monk back, especially when devs are so satisfied by their own intentional gutting of an ability that they assume it could never come back beyond its adjusted (overly limited) capacity -- see RoW-TK Monk and the lack of fluidity adjustments introduced with that skill despite making a very different playstyle optimal. We have a lot of tools that easily could have made sense and played synergetic parts with each other, but instead they get squandered because the devs only want to deal with the symptoms of skill-gap rather than its roots (i.e. by making the actual complexities of the game more accessible).
* I pointed out Star Diver in particular because it fits perfectly with Dragoon's playflow and how its optimization as a whole tends to work and feel. It's a skill that can be used at any time within a 30 second period, banked for mobility or damage, while also hitting plenty hard. Xenoglossy, on the other hand, is nice but is effectively bloat -- what could have been just a trait, an upgrade to Foul itself to cause it to change animation and deal higher damage when only the initial could be hit. Shoha, while now fitting cohesively with Iajutsu (albeit with certain new issues caused), was originally even more controversial than SsS just because it tried only to supply one purpose -- to effectively double the potency-per-tick value of Meditate -- much like the downtuned SsS and got in the way of SAM's incredibly fixed, incredibly tight rotation.