Hail of Blades on azir cant cooldown while his tower is up

While running the "Hail of Blades" rune on Azir it is unable to come off cooldown while his tower is active as every time his tower attacks ANYTHING it resets the hail of blades cooldown. And due to there usually being minions on his tower you pretty much have to choose between using hail of blades and using a tower which makes these runes even more useless on the sand king.