[FiresTFS]

The main issue I have with making the stun chance any higher is that you are guaranteed to get two attacks with it per round, so in your example, a fully upgraded Skullcaver has a 20% chance per attack to stun, so essentially you have a 40% chance every round. That's a bit high for something like stun.

So why not balance it? Stun Chance = 12 is a bit too low (24 a round?) It's still a 10-star weapon. Either that or add a secondary effect to it and up the scaling a bit. A lot of other weapons are getting ahead of it. (See: Gigantys, Hands of the Giant, etc)