http://www.wowjutsu.com/us/

The guy wrote something that compares Armory data to guild rankings. So its more dynamic than a site like Bosskillers.

What I find more interesting than the Epeen benchmarking is the absolutely tiny percentage of raid guilds that have killed something in Hyjal or BT. According to his figures its less than 1% of raiding guilds (defined loosely of course, check his FAQ).

edit: No idea how I missed that gigantic existing thread.