Stats these days seemed crazy to me, so I fixed that.
StatCrunch reduces stats on every single item in the game (even gems) so that stats are nerfed back to early Wrath levels. This is a completely visual change and you still have all the stats that you would normally.
The algorithm for stat reduction is a bit complicated. It's not just a flat half off the top or any flat percentage, it's calibrated for each individual stat and all have weights related to the item's level. You won't find a level 80 weapon being better than an 85 weapon unless it truly is better; the system is set up purposely so that item comparison still works.
This addon is not intended for the hardcore min/maxer who loves seeing numbers. I will consider adding the ability to temporarily remove the stat reduction (e.g by holding control) in the future.
Mastery is not changed because it isn't on anything other than Cata gear so there's nothing to compare it to.
Some gems have stats that are too close, so they appear to have the same increase in stats. Not a big issue but since most gems are within +/-5 of each other you can assume that the epic one is better.