Idea for an updated Ashe passive

Let's be real, Ashe's passive is only useful one or two times the entire game, and you will most likely use one of those times leashing for the jungler. Why not tweak it slightly to make it suck less.

Focus: As long as Ashe has not been damaged in the last 5 seconds, Ashe gains stacks of Focus. When Ashe has 100 stacks of Focus her next basic attack will critically strike for 250% damage (300% with Infinity Edge).

Now the passive rewards Ashe for what she was meant to do. Kiting like mad, avoiding damage, and generally being annoying. In addition, it scales into late game because more damage is always good, whereas before it would give you a free crit when you already had like 50% crit.