Make a simple macro, like this:
/cast [target=focus] shadowstep
and set a focustarget with /focus. (may also be friendly or neutral)
place it on your quickbar.
Then target any enemy player in range for shadowstep (no friend or neutral) and use the macro. You will be teleported behind your focus target you've set, no matter how long the distance is.
That's it.
With this kind of abusing, you are able to win WSG in bout 3 minutes, go
immediately to the endboss of any instance and so on. But there's a certain max range the macro doesn't work (about 200-300 yards), but in instances it will work properly.
Take a priest with you and make him Mindvision from one boss to another boss (then /assist him), so you can set the focus on the last boss if you wish so.