I was about to say lol.
I’m looking on my priest right now to see what spells grant insanity.
And as you stated that Dispels, shields etc. etc. don’t grant any.
And yes your right when you say…
But if i’m starting to pop off in PvP or 5 man and I want to use dispel and shields to help my team out while i’m in Void Form, I have to seriously consider using GCD’s to cast those spells as I am not loosing a GCD worth of damage, I could loose multiple GCD worth if it shortens my Void Form enough to end way sooner then otherwise.
I would argue that is not “fun” and “engaging” gameplay and its just bad game design and frustrating to deal with and regretful every time you do or don’t make that choice.
Anyone else (unless they are in their CD dmg window) only loose the time it takes to cast those utility spells, not any more compounding time because of it.