I know this is going to get rated down anyway, but with the level cap increases, and as SE adds more Haste gear, NIN can potentially hit 25% Haste without Haidate. Hell, they can already hit 21% currently. Since 25% Haste is an obvious cap, there's no reason to use Haidate if you're not getting the full use out of the Haste. In that situation, you'd be able to use Koga Hakama, because they give Dual Wield+ instead of Haste+.