Is Glacial Augment Ashe troll?

Slows don't stack, only the strongest slow on a target is applied. In Ashe's case, the slow from Glacial Augment is stronger than Frost Shot's base slow, but weaker than her critical slows at higher levels.

Basically, it periodically (Glacial Augment has a per-target cooldown of 7/6/5/4 seconds) gives you a slightly stronger slow for 2 seconds early on, but then becomes completely worthless once you have some critical chance.

Why get a Keystone that Ashe already has automatically in her kit?

I feel like Arcane Comet is the best on her for keeping up with any poke/deterring all-ins. It like always hits because she slows you from running away from it.

personally i go for the foot work rune,m and in secondary run cheap shot in the domination rune set, because of the cheap shots abillity being it does true damage to any movement impaired champion, she does is with every auto- attack because of her passive slowing every auto-attack

Kind of redundant on her, footwork or press the attack make more sense, especially with how good (as of now) the precision tree is.

Like MagicFlyingLlama said, Footwork or Press The Attack work best for her. After Press The Attack triggers, it boosts the power of her Q flurry, helping a little to make up for her lack of critical strike damage.

It's about as useless as it gets tbh. You're far better off using the likes of lethal tempo.