Pretty incredible. Xetrov on Farstriders took a few friends (and a pretty good Pally tank-- never thought I'd say those words) into Black Morass, and trashed all the trash. At once. With AoE. Good lord, look at all those numbers. He says he cracked 20,000 DPS, which is pretty jaw dropping.
And this is also a really good example of how Blizzard has more or less crushed AoE when you're taking on more than ten mobs-- Xetrov has almost 800 spell damage, and yet his crits are hitting at around 150-200, because with so many targets, his spell damage is pretty much negated. He's still pulling down tons of DPS (and when are you really taking on more than 10 mobs, except in wacky situations like this?). But showing numbers like 150 and 160 coming off of a Mage with 800 spell damage show pretty clearly how weak AoE can get with this many targets.