Im unsure what meta gem to use , relentless vs thundering. Ie read someother posts bout it, but im still left a bit unsure, its said that thundering has aCooldown of like 35 seconds? yet a rogue on my server claism it has refreshed itself when he has used it. So was this changed?

I've not tested the Thundering Skyfire Diamond myself as I can't find anyone Horde side on Bloodhoof to cut one. I've seem a couple screenshots of people running procwatch to monitor the procs. All screenies point to the gem being 0.9 PPM. Because of this I opted to go with the Relentless Earthstorm Diamond.

It's unfortunate as I had high hopes for this gem.