In oly you need haste, for your skills delay to decrease, mainly. If you have played some low rates you would have known about it, ecpecially when you face an other dagger.
Full buff, you already have a satisfactory atk speed, which makes your reuse delay very short. Why would you need more atk speed? For a slight boost? You sould go for CD, which is much better, especially when you hit critical skill (aka double dmg...)