There is a way that a player can skip to the final boss in Zul Farrak without completing the stair event. Is this considered an exploit? I have found a few sources alluding to the possibility of doing this on live retail servers.
Sources:
http://us.battle.net/wow/en/forum/topic/2416155251
User Tiandrah states "Sorry for reviving an old thread, but this is still a bug. I joined an in-progress ZF only to find all bosses dead except last, with the gate tightly shut. Have no idea how they did it. Blizz, if you are going to keep the flavor of the event for old times' sake, at least allow the walls to be jumped over like before. There is simply no way to finish the instance, and the problem is perpetuated, until the leader disbands the group like I did. "
http://www.ownedcore.com/forums/world-o ... ation.html
"I went up to the last boss without opening the gate (couldnt attack him tohugh )
I did this by wall jumping (look arrows)."