I don't think anyone has posted this before; feel free to delete if so.
Enter Mogu'shan Vaults, down the first 3 bosses normally and proceed to The Spirit Kings. Move into the boss room in The Repository by using the left stairs where Lorewalker Cho is standing waiting for you to kill the bosses.
Now here's the tricky part. You need a good group in order to go through with this, so it's probably better to be done with a 25man raid (or a really pro 10man).
Have a strong group of tank/healers and a few DPS enter the boss room and start the fight. At the same time, leave as many strong (self-healing) DPS as you can spare outside where Cho is standing (I assume a healer could be used too, no tank is needed). As soon as the fight starts they will be locked out behind a wall (they still get loot btw).
Every time a DPS is affected by Maddening Shout, he becomes "evil" and he is hostile towards his friendly players... including the friendly NPC Lorewalker Cho. Unless this DPS receives damage, he will remain evil, so avoid using any AOE spells near them (no need to AOE outside the boss room anyway). Single target Cho and nuke him fast using all CDs. I was locked out alone and I could only drop him to 24+mil (he kept healing up somehow, maybe from the AOE heals going on inside the friendly part of the raid).
So I am posting this so that someone can try it. Get a good group together and nuke that bloody panda. Avoid AOE damage near the affected DPS so that they remain evil, and also try to avoid AOE healing in the friendly part of the raid (that is fighting the boss) because it could be healing Cho too (I haven't confirmed this last part).
Post any results if you have the time to bother. Cheers.