Stun Mods

[Specskill]

Honestly, how do mods like Thunderclap and Crowd Control work? I honestly don't understand if they ever have any effect. I've played through 4 defense missions with my Hek, which has 10% stun from a slightly upgraded Crowd Control. I got virtually no stuns at all. The closest thing I got was Grineer Heavy Gunners sometimes stop firing completely if I keep up a decent fire rate on them. 

 

It would be great if there was some clairifcation on this. I mean is it a 10% chance to stun on each pellet or just the entire shot for a shotgun? I like stun, it opens up some fun support abilities for people to play around with, I just want it to be more specific.