It IS better than mastery on live, not only on itself, but indirectly to proc H Gurth.
This is why I try different angles over taking a tooltips word, they're shady as f*ck.
About the Gurth posts:
It procs more often for Ret in 5.0.4, how much? I'd venture and say a lot.
This is due to having and generating more holy power, lower cooldown on strikes and haste affecting said strikes, thus hitting considerably faster than prepatch.
Warriors' proc rate wasn't drastically altered, but it saw an bit of an increase.
Death Knights are proc'ing it on use of Unholy Blight per target affected, which is why they're having tentacle rape parties, although this is not intended at all.