Ashe Q stacks can be used to make more than 1 volley of W (2 stacks per additional volley)
Just like the title says basically. it wouldn't over power her because after using the stacks on the W you couldn't use the Q till having 4 stacks again. That and something else her E could do too (which i made another post about) Her kit just feels like it has not enough depth compared to other ADC. 