Eurogamer have a lenthy interview on Diablo 3 classes.
More information.There are still many things we don't know about Diablo III: how the rune skill customisation system will work (it wasn't in the build of the game at BlizzCon, as the designers are still iterating on this terrifyingly flexible feature); how randomised events will spice up the more carefully-crafted "overworld"; what form player-versus-player combat will take; and what the Battle.net online feature set will be (although, after the example set by StarCraft II, expectations are very high indeed). But the game is defined by its classes, and all four were available to play over a very extensive demo at BlizzCon. So I hogged a terminal for as long as I dared to delve into each one, and discussed them in detail with lead world designer Leonard Boyarsky and lead designer Jay Wilson. This is what I found.