Another special officer, and one that I'm looking for right now in my own guild, is the lead healer. Obviously, I'd prefer someone that's a healer themselves, that understands the strengths and weaknesses of all the healing classes. It would be absolutely fantastic to have someone make adjustments when necessary.
On Discipline in WoW
I hate to use the word "discipline" in WoW. I figure most of my guildies are adults who's spanking days are long behind them. Even the youngsters are playing a game to have fun, and deserve an opportunity to be kids. Still sometimes groups need to be reigned in, performance needs to be improved, and attitude adjustments must be made.
Your corps of officers must be prepared to take a role in these processes. Some officers are better suited than others for correcting certain issues. Officers should be able to resolve issues without being curt. In the end, even those who have been on the receiving end of "discipline" are often thankful for the correction, as are the people around them. I generally find it better to try to work with someone and explain what needs to change and why before they are removed from the guild.
Remember that your officers should be respected. They must be people you can count on to take the high road in disputes without resorting to degradation, insults, or anger. I believe that corrections should be discreet, and officers should make every effort to minimize drama. When officers remove people from the guild, generally the guild deserves an explanation as to why.
Though it may sound like a powerful position, being a good officer is a lot of work. They must attend to the guild and guild functions regularly. They do not have the luxury of being able to ignore a guildie that they do not like or playing favorites with loot or raid spots. Officers do what needs to be done.
The guild as a whole should have some input on how many officers are necessary and how they should be selected. Small guilds do not necessarily need leaders for each class, large guilds may need additional officers to help maintain order. Some guilds elect their officers while others select the best raiders or best in class.
Good leadership can make or break a guild. Guildies don't have to like all of the officers in a guild, but they should respect them.
WoW.com offers a plethora of information on guild leadership and guild membership. Be sure to check out Scott Andrew's Weekly Column Officer's Quarters and keep an eye on the community with Mike Schramm's Guildwatch.