For those who missed going to BlizzCon 2011 or watching the livestream here are a few videos of L90ETC live performance. They played songs based on Diablo III, StarCraft II: Heart of the Swarm and World of Warcraft: Mists of Pandaria.
L90ETC is composed of Blizzard CEO Mike Morhaime (Bass), StarCraft II Lead Producer Chris Sigaty (Rythm guitar), Alan Dabiri (Drums), Dave Berggren (lead guitarist) and Blizzard Senior Art Director Samwise Didier (vocalist).