Here is my way of making stormwind dissapear and getting into the Champions Hall at the same time. Im not sure if anyone has posted my way but its fast and it works.
1) From Stormwind Head to the area were the gryphon master is.
2) In that ledge area that he is in you will see some barrels one group of them have them stacked ontop of each other. Jump on them so your on the very top.
3) From ontop of the barrels jump over to the ledge and run around the ledge till you get to the very end of the ledge.
4) If you look down you will see another ledge jump straight down to the lower ledge.
5) On that lower ledge start making your way to the mountains.
6) Once you reach the mountains there will be a spot were the mountains and the concrete wall meet and make kind of a V shape.
7) This is the hardest part of the whole proccess. The trick is to hold W down so your always running forward. With W held down start hitting the space bar to jump. I find that hitting jump about once every 0.5-1 second. With a little bit of practice its very easy to climb the wall.
Once you get to the top of the mountain, you can make a jump and get up ontop of the concrete wall. There is a little lookout tower thing up there. 9) From ontop of the tower you can either slow fall into the Champions Hall or jump down from the wall towards StormWind.
Any class can get into the Champions Hall as long as you have the parachute cloak.