As I'm currently deciding on which blacksmithing specialization I'm going to choose in TBC, I've wondered how exactly stuns from weapons such as the Deep Thunder are treated in regard to diminishing returns.
I know that Blizzard has put mace spec on an entirely seperate timer, in order that it does not interfere with your controlled stuns from abilities. But what about those weapon procs?
If they trigger your normal diminishing return on things like intercept that would be quite detrimental to the usefulness of such weapons in pvp, so I'm looking for some definite information on this subject.

There are basically three possibilities:
a. weapon proc stuns share the same DR timer as mace specialization stuns
b. weapon proc stuns share the same DR timer as your normal ability stuns
c. weapon proc stuns have an independant DR timer

Now, which of them is true?

From what I've seen the proc on Dark Edge is on diminishing returns with itself only. I've never been mace spec or had a weapon with a stun proc so I can't comment on that.

Letter A is the correct answer.

There are two general sets of diminishing returns - "controlled" stuns, and "chance" stuns. Controlled stuns include all 100% chance abilities like Charge, Intercept, HoJ, Bash, and the like. Chance stuns are everything that has a less-than-100% chance to proc - things like Revenge Stun, Mace Spec, Seal of Justice, and weapon Chance on Hit: Stuns target effects.

The only exceptions I can think of off of the top of my head are the Rogue's Cheap shot and Kidney shot.

Dark Edge of Insanity's proc is a disorient that is flagged to not break on damage. It is not a true stun, which is why it does not interfere with other proc-based stuns.

Cheap Shot is on the same "controlled" stuns timer as many other abilities. CS someone a warrior just charged and it lasts half as long. Kidney, on the other hand, I'm pretty sure is another case where it's only on diminishing returns with itself.

Dark Edge is not a stun proc.

Best info to date is that there are 2 sets of diminishing returns. 1 for controlled stuns when you use an ability that will stun 100% of the time, and one for uncontrolled, being any ability or proc that has a chance to stun.

I don't know if this is the case on live or not since i haven't been prot spec'd since well before shield slam was introduced, but currently on beta mobs quickly become immune to imp revenge proc.