Ashe's Passive

I need to understand why anyone at Riot Games thought that Ashe's new passive was good game design. My primary, driving concern on it is that there is zero counterplay outside of tenacity. It costs no mana, it requires no items, there's no threshold at which it switches on, and you get it at level 1. The only skill it requires is your ability to understand that an enemy is within auto-attack range, and your physical dexterity at moving your mouse over that enemy and right-clicking them.

I just...I need to understand why this was not only considered a good idea, but implemented on live servers.