If you are using his dash attack to get into melee range you are doing it wrong, his dash is a finisher as it resets -if you kill someone with it- so you want to be using it as a finisher to have it isntantly off cooldown.
You want to get in close and then use the combo attack which each successive attack button cancels the animation of the previous, the combo is as follows - Left click -> Melee -> shift (dash attack) which will kill squishy targets nearly instantly and reset dash for the next kill.
For medium armored targets you need to spend a little time peppering them with ninja stars before the combo.