At grand storm's low health and lack of access to shield breakers relegate it to bottom position. It isn't helped by the fact that it's damage boost is pretty much the same as other schools, it isn't at max accuracy even with full commandeer gear and it's lore spells offer almost no relevant utility.
At max it's the same old problems of low health, lack of shield breakers and lack of utility. That's further compounded by the fact that shadow spells and pierce jewels give every school low pip burst potential that easily wipes out 50%+ of storms health in a single go.
The storm schools universal trashiness at virtually all levels coupled with KI's complete apathy towards the situation (despite literally years of feedback) is one of the main reasons I have almost no motivation to play.