This expliot requires the following:
A priest with Mind Control
A rogue with Shadowstep
Timing
It's pretty simple to explain, but more difficult to perform.
Make the priest Mind Control the rogue, as the cast is just about to finish the rogue uses Shadowstep, when the priest notice that the speed increase from Shadowstep is just about to run out - he cancels Mind Control
This requires some timing, but you'll get it pretty quick
(This is of course working on retail)