It certainly doesn't seem like an efficient build, but it would definitely have it's uses. Personally, if I were going to go with a high aspd build I'd get low 9x agi. 190 aspd for critlock is serious overkill for a sinx using katars (that would be 10 "hits"/second including the offhand hit). Though less extreme, this would free up a lot of stat points for a more rounded build.
Sinx's with over 90 agi can be stun immune (without orc hero sunnies) for a few hundred mil, or can have 90% stun resist and also be able to quite easily get 50 vit. Even in large-scale fights you shouldn't be dying to stun easily with this much resist.
The point about breakers is moot. Mastersmiths barely even break anything these days. If you ask people, all their shit is broken by acid bomb. A 5% chance to break one weapon or armor while meleeing is a waste of time for a sinx.
However, the new katars do look good. I don't know what stats affect the chance/duration of critical wounds, but a crit sinx using a +9 wild beast claw will be doing 1-1.5k crits at 187-190 aspd with EDP and full buffs while also inflicting a -40% healiing/potting ability on the target. That sounds like it could take down/help take down a tank very quickly.
Again, probably not as efficient as an SB sinx, but I'm sure a sinx like this wouldn't be horrible as long as you have the gears for it and a good build.