Addiction can be dangerous no matter what it's for. It's good that you're trying to understand your brother, and I really hope that you'll be able to reach him and pull him out of the shell of the game. :)
I've always found that warriors are one of the most difficult classes to master, but asha, who is my mate, has really enjoyed building one. For myself, I'm much happier with a warlock or a hunter, although I've been trying all sorts of different classes.
I like the Draenei for the way their area is set up - it's very easy to build your character up all the way to 20 without ever having to go to the mainlands. My human warlock wasn't quite as lucky in that.