Its what Cirrus says, I added the Str, after the Dex.
Dex, is the Dex I kept increasing by increments of 10.
Pre-ASPD, ASPD before Slow Grace.
Post-ASPD, ASPD after Slow Grace.
Str, the amount of Str I started to add after my Dex was max. (Considering IG on the skill description it reads Str affects ASPD, so I thought I might as well give it a try.)
Agi, Agi affects the walking speed, I thought maybe its a combination of the two that affects ASPD, but at this point...I got fed up. Lol. (Agi, when Dex is already max and Str is where I last added)
As for the class, I tested it on your typical breaker/pvp sinx builds. However, there were two Gunslingers and a Priest, the results were still the same.
From my tests the greatest amount Dex reduced ASPD is only 2.5% (Which is the max 5 point reduction)
Also, the reduction rate isn't even linear, so I can't really say how Slow Grace reduces ASPD.
At the points where ASPD was effect Dex was increased by: 170 (191) then 210 (190)
Unless, the rate is going up 40 * 4.25 = 170 , 40 * 5.25 = 210, then the next one is 40 * 6.25 = 250. The next change in ASPD being 250 Dex more, there is no way to reach 630 Dex just for the 3% change in ASPD.