I mean, it does have its uses, but it goes against the basic principle of the Kraken, which is to strike from afar, away from the Hunter’s weapons. Aftershock, beyond requiring you to be close to the Hunters, has a quite limited reach, even on tier 3, and the damage is negligible when compared to the other, much safer skills.
You can scare Hunters when they get close, you get cornered, or pulled down, but… As a Hunter fighting a Kraken, I totally ignore the Kraken’s Aftershock. In fact, I try to make use of the time it wastes charging it up to do something nice like chipping its health or reviving someone.
It’s much stronger to have all skill points equally distributed between the other skills. That is not to say that you can’t play effectively with Aftershock. it just means it’s better not to.