TLDR: Omen of Clarity Theorycraft
I filtered Uday's
WWS log (the entire log, not just the PW fight) to show just SF and Clearcasting (= Omen of Clarity). I assumed that any clearcast within 0.5s of a Starfire was caused by the Starfire. This is optimistic. Some of those could have been caused by an instant cast.
The WWS reports 707 SF hits. My eyeball counting shows 49 OoC caused by SF. That is a proc rate of 6.93%.
If the actual proc rate is the 6% reported on wowwiki and wowhead, there is about a 13% chance of getting 49 or more procs in 707 trials. Not bad, particularly since some of those procs probably belonged to MF or IS.
I don't know what Uday's actual cast times were. If we use a very optimistic 1.5s, and assume 3.5 procs per minute based on actual cast times (not base times), there is about a 4.6% chance of getting 49, or fewer procs.
At 3.5 ppm based on
2s, chance of 49 or fewer < 1/50000.
3s, chance of 49 or fewer < 1/6e15
3.5s, chance of 49 or fewer < 1/6e22
I believe WrathCalcs and Rawr are using the 3.5s value. From looking at the code, I believe Simulationcraft is using the 3s value. If I'm correct, those are giving OoC too much credit. At low crit rates, in a mana-constrained fight, Rawr recommends SF-spam (with OoC), versus IS SF (without OoC).
I'm guessing that the real number is a fixed 6%, which is the number that feral cats report (and OoC has a much larger impact on them, so they have a large incentive to get it right).
Using the same method to look at MF. I see 7 OoC procs from 84 casts (8.3%).