So then I have a question for everyone here.
If you have seen WoL (
http://www.worldoflogs.com/rankings/...f_Thunder/hps/), in the 25MH one of the top disc priests (from the guild Vigil) looking at his stats (25% Mastery, 13% Crit, 6.5% Haste, about 20k int, 29k SP and 13.5k spirit) is kicking butt, not just on the logs, but is about 20k more than the second disc priest in his group and yet he has been consistently the top ranked in the logs.
Now the second disc priest in the group has the following stats (19% mastery, 20% crit, 3.2% haste, about 20k int, 27k SP, and 12.5k Spirit)
There is a 3ilvl difference in, they both have the same trinkets (Horridon's and Spirit of the sun). The top example gems almost entirely spirit, while the other a mix of spirit crit gems.
There is almost a 20-40k difference on every fight. Also looking at spell use differences as well.
In fact looking at other priests there, none of them have crit > mastery, but they all have over 12.5k spirit (some as high as 15k).