Question - do you have to stop to use another skill while auto-attacking on another char? IE have to stop to self-buff while auto-attacking with a Sniper, or LK, or whatever. My game isn't functioning right now so I can't test this myself... but if you can still do that on other chars, then there's no reason why it would be that way with Hindsight. The reason is really simple - Hindsight is not what is causing you to auto-attack, that's a normal mode of attack regardless. The Hindsight skill is only the proc chance for bolts. So if you can still use a skill while auto-attacking on another class, then Hindsight is broken and interfering with normal attack mode. Even with an after-cast delay present after an auto-casted bolt (normal behaviour, not applied to subsequent auto-casted bolts), you should still be able to use other skills, even if they stop you from continuing to attack (also normal behaviour).
Someone wanna test this?
Edit: The comparison to Storm Gust isn't the same, because Hindsight is not a damage-dealing skill in itself. It's basically just a trigger to automatically use your skills.