Her Q desperately needs to scale with at least .7 AP, I feel her base damage on it is incredibly low compared to other AP carries. Right now at .5 her Q cant clear caster minions even with it maxed. Even increasing base damage by 10 or 15 and AP scaling to .65 would make her better.
Im going to address the skill cap thing quick since I know its coming..Cass has a higher skill req. Yet her q is fairly easy to land, just about as easy as syndras Q imo (Cass doesnt have nearly as long of a delay). Cass's Q is also a 3 second CD with 15 more base damage than syndra AND scales with .8 AP
Take this with a grain of salt, this is my personal opinion.