1. It's all your fault.
Just by virtue of your new position, you now can expect that ultimately throngs of passionate WoW players will consider you the impetus for all that is wrong with the world (of warcraft). When a class feels underpowered, it will be because you hate them. When a class is overpowered, it's because you hate every other class, and when that overpowered class is then balanced, you nerfed them because you hate them. Don't bother trying to respond to these assumptions rationally. They are made by irrational people, and logic has no power with them.
2. Performance expectations are 100%.
Like the old saying about umpires, you are expected to start out perfect and work your way up from there. Despite all the newfound blame you are receiving for the condition of the game, you can't expect to get any credit when things go right. You will however be called to task for any mistakes made by you or anyone else under you. And if you ever change your mind about a design direction and move even slightly in any other direction, someone will have posted that idea years ago on the forums and will say "We told you so".
3. Sometimes, the players are right. Sometimes.
Good communication with the playerbase leads to good game design. The catch is sifting the good communication from the oceans of "omg buff me" or "don't nerf me bro" and other such useless information. But the good communication is out there. Please look for it.
4. Anything you ever say is a promise.
Anything you speculate about changing (or not changing) will be automatically considered canon, and will be referenced as such.
Unless you specifically say it isn't a promise. Then it's only kind-of a promise. Either way people will still expect it to come to pass as they envisioned it, as though you swore a blood oath.
5. You can't make everyone happy.
The day everyone is universally happy with one of your decisions, get under your desk immediately, because the sky about to start falling on our heads. There will always be a vocal opposition to anything you do. You could literally start offering free money to all wow players tomorrow and someone would find a reason to be against it. Not that some criticisms won't be fair and legitimate, just know that there will ALWAYS be criticism.
6. Don't try to force fun.
Try not to lose the focus on simple enjoyment. Sometimes it's difficult to determine what will be the most fun for people, balanced with how long it will be fun. But remember that fun can't always be dictated or shaped to meet with your ideas. There will be times when you make an unpopular decision in the interest of creating a certain experience. That's fine. Just make sure you don't become so entrenched in creating that experience that you forget to ask how many people are enjoying it.
Well I think that covers all the stuff I can be helpful with. Good luck in your new position!