From the guide:
"2.5 Reforging
Any items with both mastery rating and crit rating should NOT be reforged; they are perfect for feral dps already!"
I was playing around with Rawr this weekend. I have some items with both mastery and crit, and it was telling me I could get 10 to 20 more dps by reforging their hit to haste. Rawr was saying at my gear level that crit and haste were very close, in fact they were flip flopping as to which was better as I swapped pieces in and out.
Don't know how accurate kitty Rawr is at this point. Strangely it works great on one of my computers. But, on the other one all the gear I am wearing comes in, but none of the other gear does.