Make Gathering Storm useful for hybrid

Gathering Strom right now is useful for late game champions that benefit through only ad or ap, but not so much for champions going for a hybrid build (who is usually looking for late game like). It should be nice if it can also benefit hybrid. For example:

if the bonus ad and ap difference are less than 40 (or if the potential damage output difference between ad and ap is less than 30%) then Gathering Storm will give half stats of both ad and ap.