I am sorry, Ooshima, you seem to be a very competent bard and ninja, but you have no clue about math.
I do not mean to insult you there, it is just that the the logic you try to apply is, well, illogic.
As others have pointed out, you are going to waste more off your GCD if you lag for mudras and lower your GCD. Take extreme exemples to convince yourself: let's assume that you take 3 second to complete a mudra, would you rather have a 1 sec GCD or a 3 sec one ? Well the second case let you do your full mudra during the Off GCD time, while in the second case you waste 2 GCD waiting for the mudra to finish.
The issue is you assume more actions is better, but you fail to take into account that if you do less actions you have more det / crit so each actions count more. If i have on one hand a GCD of 1 sec and on the other 3 sec, the 3 second GCD person must be assumed to deal 3 times more damage per action, as the loss in time is compensated by more crit chance and higher det.
You also mention that you have to let your dots fall sometime for 1-2 sec on time when using no skill speed. I agree. It is not an issue. If you use as much skill speed as you say you do, you are going to clip them sometime for 1-2 second instead, which is about the same loss. It will not be all the time, but you will not let them fall everytime in the previous case either. Trading one evil for another. I provided the math for this on the previous page, check it out again if you are unconvinced.
As far as i can tell, from my testing, for nins, and due to their lack of TP issues, det, crit and SS are all close to one another in term of dps increase. I would advise anyone to aim for just the accuracy they need above any other considerations. Then, from my testing, det seems the most efficient of the 3 stats, but only by a tiny margin (10-20% i would say), and thus i would rather take SS or crit over det if it means being where i want to be acc wise instead of 15-20 lower or higher. In any case, i have yet to see a compelling argument for stacking out SS until any kind of treshold -- 2.15 GCD works just fine, and so does 2.0, and so does anything in between ; i would not want to go much higher than 2.15 or much lower than 2.0, but since you can't anyway, it's a moot point.