Let's see if I can give a brief overview. First is the panelists, these guy's names don't get out there too much but them along with the rest of the amazing artists help to create the world and do a kick ass job of it too.

Art Director - Christian Lichtner
Lead Character Artist - Paul Warzecha
Senior Artist (animation) - Nick Chilano
Tech/FX artist - Chris Haga
Environment Artist - Nathan Bowden
Sr. Environment Artist - Patrick Stone

The first part was with Paul and went over "character" creation, in this case the Fallen monster family. How it went from early concepts to more recent concepts, modeling, animation, and texturing. Imp, Shaman, Hound, Lunatic, Overseer. How their silhouettes define them outside of their design/abilities. There was some hint that the family revealed thus far may not be complete.

Then he went over the creation of the witch doctor, again from concepts through the modeling and texturing process. Through some of the earlier artistic designs of follower/helper type skills such as the wicker man and fetish that would have rode on the witch doctor's back (both of which were either scrapped or transformed into other ideas).

Then Nick went over animation, how the animation team pours over design docs and references to get an idea of how the creature/character should move and react, but ultimately just relying on the fact that "Jay Wants Awesomeness!!" There were videos showing examples of animation progressions, reference videos used to help the animators (we don't mocap), and some final products.

Then Haga went over Tech/FX. Some of the things the tech art team does: Rigging, Character Implementation, Data wrangling, Debugging, Lighting and Light Map creation, Custom Tools and Scripting, FX, Design/Implementation. He went through how some of the monk skills were created, and the progression of them getting more and more awesome.

Pat Stone went over dungeons, from concepts and theme/lighting/mood to rough models, textures, refining passes, etc. How areas are created in "gray box" modes first, which are rough block outs of rooms to test how they play before any texturing or detail work goes into them. He also went over the concept of "showcase rooms". These are larger rooms that are made (essentially) first and encompass a lot of what will be going into the dungeon to serve as a style guide for the rest of the dungeon. Everything needs to blend seamlessly so a large central focus to build from helps to keep the dungeon feeling cohesive. And of course a brief bit on how dungeon rooms are randomized.

Nate went into exterior, taking the concept of the Stinging Winds (playable area at BlizzCon) and how the colors/shapes translated into playable space. How they wanted to keep a lot of depth in the zone with the rocks as well as cliffs and mining operations. Then probably my favorite part, and completely unfulfilling to type out, was a video showing Nate taking a concept of a small village/building in the Stinging Winds and building it in-game using our editing tools. He walked through how he builds out areas from big items to the smaller details, and then it's handed off for lighting passes, and the panel ended with run through of the area we watched him build in-game looking all pretty.