I got locked outside of the gates to Gothik the Harvester when I told one of my party members to come next to the gate and see if I could shadowstep through, and it worked, and this have never been worked before, so patch 5.4 must have broken Shadowstep LoS.
Me and a friend started looking for potential spots to step to, so we tried Utgarde Keep, Naxx, BWL and UBRS.
There is a few restrictions however. The target you shadowstep have to be a enemy mob or a player that already got through the object. You have to force the npcs half way through the gates for it to work. You have to hug the object to get inside it while you shadowstep, otherwise you'll get a "LOS" error.
Watch the video to see what I've figured out so far.