What you need for this exploit to work:
Rogue with the subtlety talent Premeditation
This exploit allows you to pull an NPC from long range and from stealth.
First, go into stealth and target the NPC you wish to pull. Get in range enough to use Premeditation. Cast Premeditation, then sprint as far as you can in 9 seconds. Remember, the combo points from Premeditation only last ten seconds. When you are as far as you can go while still having combo points, cast Slice 'n' Dice. This will pull the mob to you.
Slice 'n' Dice has a range too but it is much longer than the standard abilities in the game. I have only messed around in regular PvE instances with this bug. This might open the door to countless boss exploits!
If you do not have Premeditation, you can attack the target NPC and gain a combo point and then vanish. Then proceed as normal with the Slice 'n' Dice at range. (unconfirmed by me)
Enjoy!