1/3 chance of proccing is a pretty solid rate. That means every 3 skills you cast 1 of them have a chance of proccing this. So once every 3 seconds. But that doesn't mean that you won't get lucky streaks where it procs back to back to back. That's just how RNG works.
However, I have noticed that the skill is producing a phantom proc sound even when it doesn't proc. I've gone to cast a proc after hearing the sound and it started a hard cast instead.
Outside of cleaning up the potential phantom proc sound, the skill is fine and really doesn't need to be nerfed anymore because "it seems that the activation rate is way superior."