Slave to the Grind

http://www.youtube.com/watch?v=IMUIY_jxkwU

That is funny as hell hope they patch that soon

They apparently applied a hotfix right away so that vengeance caps at max health now. That's still really high but should keep people from getting up to 2M+ AP like this guy was.

Not saying it didn't happen, but the one glitch I saw in both this vid and another one they did was "Windsong" and "Windsong faded" ... they may have solo'd it but I'm hard felt to think its a lvl 80 and if that comes into question, so does so much more. I do have to admit it was fun to watch though

There's a couple of issues at play, explained in some detail here. tl;dr version:

1. He's level 80 in ilevel 400+ gear (for example [item]87426[/item]), so he has much much better gear than anybody would have had at the end of Wrath (Heroic LK items were ilevel 284). By being 80 and avoiding the combat rating dropoffs that occur at 81, his secondary stats were probably all 80%+.
2. A whole bunch of stuff, such as [spell]20165[/spell] and [spell]20925[/spell] scale with AP.
3. At 2M+ AP and being as near to avoidance capped as the game will allow, you pretty much don't take any damage.