A couple of things to make Ashe more relevant.

Focus (Passive): As the battle rages on, Ashe gains focus. For every second in combat, Ashe gains 3/4/5% Critical Strike Chance. Focus reaches a cap after 5 seconds of combat, and resets after 5 seconds of not attacking or being attacked. Context: This change makes it so that Ashe is rewarded for staying in combat as opposed to not attacking at all while retaining the critical strike theme of the existing iteration of Focus.

Frost Shot (Q): While active, each of Ashe's basic attacks slow her targets. This drains Mana with each attack. Toggle: Basic attacks slow enemies by 15/20/25/30/35% for 2 seconds. Each consecutive Auto-Attack against a target affected by Frost shot is slowed by an extra 5% of that value while Frost shot is Active (maximum of 25%). After attacking another target, however, the slow resets and returns to 15/20/25/30/35%. Context: Adds additional decision making to the ability (increased slow vs. engaging multiple targets) as well as providing greater reward for using Frost Shot (increased slow for continuing to keep Frost Shot active vs. simply re-applying the slow).