If you take the skill "Ranged shadow impact" you are no longer able to combo/chain cast shadow missile. After taking this skill each and every cast of shadow missile causes your character to stop for a few seconds before being able to start a new attack chain and you are never able to chain cast shadow missile again. It is pretty game breaking and a real pain in the ass because you can not get "Storm" with out this skill. So much for basic QA bug testing when a skill tree this simple doesn't even get tested.
Bug with skill "Ranged shadow impact" on PC official steam copy