Has this always been here? I wouldn't be surprised if it has. There's so much to look at in the game, but I've been coming to Karazhan every week for over six months and this is the first time I've noticed this. I did not see a wind rider, but the Horde could use this flight path, too. It reminds me of Blackrock Mountain where the entry to Blackwing Descent is on the terrace where the final battle with Nefarian occurs in Blackwing Lair.
Still, we got all excited earlier in the year when it was noted the cobwebs had been removed from Karazhan. Could this be a precursor of something coming? If you want to check it out for yourself, it's about a quarter of the way down the tower from the top. There's not enough room in the space for a stone or a lot of people entering the portal."