[Shujin]

To be fair, it DOES consume the stacks, so if you use it you might lose another Storm Cast. So I do not think it's terrible.

Something I wanted to suggest for Aquamancer though is a passive skill that allows you to turn on and off crest consumption. Sometimes some of the crest effects are simply not desirable at that very moment. It could also help with this a bit.

But yes, the effect as it stands is a bit too expensive for what it does.