Originally Posted by
Angelo WoW
You're not thinking it through all the way I think.
EVEN IF you were to have a voidform so perfect and utopic as you describe it, without running into ANY errors, you STILL wouldn't want to take Shadowy Insight on a 3 Target Cleave. You forget the important factor of gaining haste every 1 second of a consecutive voidform, and this means that our globals become shorter and shorter every second. This, in return, means that EVEN IF (again) we were to have such a perfect Voidform, we simply wouldn't be able to cast Mind Blast after a certain amount of stacks anymore properly, as our VB is already off of its cooldown again, and obviously has priority. That being said, Shadowy Insight will then literally get in the way. Why? Because there's no way you can count on it proccing when you need it, meaning you could very well be casting a Mind Blast, and then MID CAST your stupid Shadowy Insight procs. You have now wasted about 1 second of precious time you could've been using otherwise, run risk of dropping voidform, and on top of that most probably didn't keep void bolt on cooldown. If this happens more than once you begin running risk of dropping a DoT, and then chaos unfolds.
That being said, and after considering this issue even further: Without AS on a Cleave fight you wouldn't even generate enough insanity to have a long Voidform. So even if the above was to happen, or even if we were to have a sweet and perfect voidform: STILL no Shadowy freaking Insight, because it's legitimately useless on cleave fights. A proc that's worth 12 Insanity (FotM considered) for a passive that easily generates 30 insanity in the same time frame?
Shadowy Insight is something I'd never take in a cleave encounter.