So, wait until you read Ashe's new passive then:
Every 3 attacks, Ashe fires a large arrow in straight line and if it hits an enemy champion, it strikes a lethal blow, dealing true damage.
For each stack of Slow on the target, Freljord Arrow - Guillotine of Doom deals an additional 20% of magic, physical AND true damage.
The cooldown is refreshed if Freljord Arrow - Guillotine of Doom kills the target.
And you though Ezreal and Graves were annoying ADc/Casters? Wait till you see this applied on Ashe, then.