Most of the day is spent in communication of some sort. We'll have formal meetings where we review a current talent tree. We have just tons and tons of discussions of "Hey, guys, I had an idea," or "Hey, I can't solve this problem. Any thoughts?" We do work quite closely with the programmers implementing things like the new talent UI or the new scaling spell model. We also work closely with the artists coming up with new spell visuals. Our QA department is constantly trying to sort through what the design of the moment is, and they do a great job of triaging the totally broken things from the "fix this before we ship" things. The community team brings us concerns that they have seen on the forums or from their interactions with players. This is particularly true for the non-English forums, because my non-English for one is sadly lacking. History geek that I am, I studied Ancient Greek in college, which serves me about as well in day to day life as you probably imagine.
GC's got friends in every town and village from here to the Sudan. He speaks a dozen languages, knows every local custom. He'll blend in -- disappear -- you'll never see him again. With any luck... he's got the Grail already.
GC: Does anyone here speak English? Or even Ancient Greek?
There aren't many typical days. Sometimes we will spend literally hours discussing one problem. The last few days it has been the paladin rotations. We'll throw things on white boards, send out some ideas to guys not actually in the office, try out some stuff in game to see how it feels, and get feedback from anyone who has recently run one of the new dungeons or tried a new BG. We interact a lot with the community outside of the building, visibly on forums like this one, but through email, IRC and even in game. There are a lot of excellent PvP and PvE players with whom I regularly correspond, and I want to call out any of you reading this and thank you publically.
Overall the environment is very collaborative. The team as a whole (by which I mean the artists, programmers, producers and everyone else) don't get enough credit for the design decisions that go into the game. In many cases, my guys are just the implementers, but the ideas and feedback come from everyone working on WoW.