Cut the duration and cut the cd on the stuns. The stuns themselves aren't powerful from an outside perspective, but what people are saying is the duration is too long to where towards the end of an expansion you're getting wrecked inside of a stun.
If you cut the cd along with the duration it's a slight nerf, but still the same net result. Honestly I think it would be fine with a 50% cd reduction with a 40% duration reduction which is in the long run equal even though it seems like a buff.
I swear I have a feeling of deja vu even typing this right now. I'm too lazy to do a forum search.
Its an interesting idea but it would need a fair amount of work. KS in particular would become a completely different spell with this change. 5cps for a 3.6 second stun may not be worth it in many situations. A 10 second CD KS would probably be used primarily as an extra interrupt and would make rogues into even more of the premier caster lockdown class.