User blog comment:JmLyan/Katsuhe, the Maiden of Ionia/@comment-5663427-20140821181847/@comment-7481207-20140822134828

The 60%  reduction of the cooldown is not additive with ordinary CDR, is it reduced from Elusive Dance's CD after CDR, so roughly 3 seconds cooldown is the lowest amount you can get it to.

@ Primus: Ashe's and Shaco's slows indeed doesn't have any damage themselves, but they are both on-hit, so good luck hitting these without dealing any damage. And Twitch's slow applies stacks of his passive, thus also causing damage.