Disclaimer: I DID NOT find this exploit myself, but I think it's important to share such things with the mmowned community. And please excuse me for my terrible english btw.
Brutal Earthstorm Diamond
+3 Melee Damage and Chance to Stun Target
Requires at least 2 Red gems
Requires at least 2 Yellow gems
Requires at least 2 Blue gems
Item Level 70
"Only fits in a meta gem slot."
Brutal Earthstorm Diamond - Item - World of Warcraft
Advantanges:
-It can interrupt casts
-When you spam FoK To put up mind-numming it can aoe stun people
-It can slow people down
-It can proc over itself and on multiple targets
Disadvantage:
-You don't control it
-It has a 1% proc BUT!
Mutilate uses daggers,
Mutilate uses slice and dice
Mutilate hit's with both weapons
FoK can hit many targets
Some people will probably argue that it's intended and/or common sense, but the past tends to show that such items are hotfixed quickly (silencing blades from Scholomance on S5 DK anyone?). If this reason isn't enough, see this as a guide (or feel free to put this in the guide section if you are a mod )
Have fun while it last ! ^.^