While designers typically have different goals in mind and sometimes overlook things that crafty players find out, I think it's a bit arrogant to assume that they don't know how to play the game they have created.
Though some decisions indeed range from questionable ... to bat shit insane.
Then again, they are Japanese, some measure of insanity comes with the territory I guess.
That's a lot of practicing in order to get the statistical fluctuations under control.
I always get a good chuckle when some poor sod gets +100 crit on his gear and subsequently runs to the dummy to find out whether he does more damage now. :S
Even simulationcraft had difficulty with that one and there I could run 100k iterations of a 10 Minute fight.