Pulled this off of WoR quoting Ghostcrawler:

The WoW Design Team

Quote from: Ghostcrawler (Source)

There are different types of designers. Some work on quests, encounters, world events or zones. My team works on classes, items, tradeskills, UI, PvP, combat and pretty much most of the crunchy bits of WoW. It's a great team of very talented players and they don't get the recognition they deserve. This is partially because some of them wish to remain anonymous. (Shameless plug: we are hiring an item designer. Check the hiring portion of the site for more details.)

Within our team, nobody owns a particular class. We all work on them together and nobody make a change (at least a serious change) without getting consensus from everyone else. We draw on our own experiences, community feedback, internal testing, data collected from the live game, and correspondence with friends, guildies and other players whose opinions we've grown to respect.

We also interact a lot with the other designers, because they all play the game too and many have a great deal of raiding or PvP experience. They come to our meetings or just drop by with an idea or a piece of feedback. That goes for the rest of the WoW team, and in fact all of Blizzard. We are extremely collaborative and not particularly hierarchical.

Our designers tend to be fairly technical as the industry goes, and some of us know a little programming, but typically we aren't writing actual code though we do write scripts and make data queries if you understand the distinction.

The programmers are a separate but equal department. They do write code and they are extremely talented, sometimes intimidatingly so. We ask them for new features or code changes that would improve the game and they tell us what is feasible, what is risky, and suggest alternative ways to get what we want. They are all gamers too so it's really a back and forth process as we work on an idea together until we come up with something we are happy with.

The process is similar for interacting with artists, or really any other component of the team. The big secret of WoW's success is that Blizzard just manages to hire very, very good people who "get it."

 

This is a very a insightful look into the team at Blizzard.  Think you've got what it takes to hang at Blizzard? Go check out that item designer position :)