An even-handed approach
I think one of the most important things for guildmates to do is not dismiss nerf claims; instead, encourage patience. It's easy to brush off a player's complaint when she feels less powerful, and some might even feel it was a nerf that was long overdue, but for the nerfed player, she feels as if she's instantly dropped down a few rungs, and she's frustrated at the limitations of her new role. Another problem is that groups and guilds try to optimize, since there are only so many slots to fill. Nerfed players end up feeling like the kid who didn't get picked for the kickball team.
The best thing guildmates can do is be sympathetic without enabling a Henny Penny scenario. Yes, nerfs are a pain, but they're usually not as bad as they might feel, and they certainly aren't the end of the world.
Perceived roles vs. actual roles
When you're grouping and raiding, there are the typical roles, like tanking, DPS, healing, and utility, and then there are specific roles for specific encounters. If you're a DPSer, it's important to crank up the damage during a key fight, but it's equally important to handle the little tricks and twists that occur, like managing adds, interacting with certain objects, and moving to avoid certain attacks.
I always tended to downplay parses because they won't ensure success if your raid can't execute. In fact, there are lots of fights with scripts that actually nudge you to do the opposite of what you're used to doing. If you DPS too quickly in these quirky fights, for example, you'll spawn too many adds too soon and make it a lot harder on the raid. Or if you heal someone with a particular debuff on him, you'll trigger a massive AoE. Your newly nerfed Wizard might be grumpy because he's not tops on the parse, but he might play the crucial role of keeping an add rooted while the raid handles something else. It's worth reminding guildies of that because it's often the little things that make for a successful raid.
Roles outside the game
Another thing that guilds naturally tend to do is hold an appreciation for the person rather than the toon. When Nerfed Tankman logs in, guildmates are happy to see him, regardless of whether he can still hold aggro on 15 mobs or not. Long-running guilds usually end up with the same core group of players and have grown to avoid overreacting to every bump in the road, be it a class nerf, content change, or even an issue within the guild. And they also adjust well, taking into consideration the full bag of tricks that each class has. It's amazing how many times we hear about how you "need this class" or you "have to have this amount of damage" in order to defeat a mob, when in actuality, a seldom-used ability or alternative strategy works just as well if not better. Guilds that have been around for a while tend to almost form a brain trust that can tailor tactics and strategies to the strengths of the members, regardless of class nerfs, and as a result, they help everyone focus on problem solving rather than the misery of the nerf.
Believe it or not, guilds can be a useful lobbying group if there is a nerf that seems too heavy-handed. If you have a healing brigade, and there's a clear disparity among the different healer classes, for example, you probably have some good data to provide in the form of parses and member feedback. That's worth passing along to the development team, and if done in a reasonable manner, it can actually help the devs double check the nerf and perhaps balance things out better.
Fun balance vs. class balance
A class nerf can really suck the enjoyment out of gaming, and while many nerfs are probably necessary, they can cause players to get so frustrated that they decide not to play that class any more. The question then becomes, do they stick around and play another class or do they leave? And if they reroll, do you let them raid with the new characters? It's up to each guildleader to make that decision, but I've grown to accept players rerolling, as long as it doesn't become such a pattern that the player is basically using the guild to gear up a collection of virtual Barbie dolls.
Nerfs aren't fun, but they're a necessary part of the game. It's frustrating to feel like the weak link, and it's no surprise that some players will give up on a class completely as a result of having been nerfed. I've played a Ranger, so believe me, I know the frustrations! A player can go from feeling like the center of gameplay to feeling like he's playing second fiddle, and even if it was a necessary adjustment, the abruptness (and sometime stealthiness!) of the change can be hard to accept. However, guilds can help out a lot, often with very little effort. What it comes down to is making your players feel needed, and well-run guilds create an atmosphere where everyone feels like she's an important contributor to the guild's success. Hopefully, guilds de-emphasize the value of a class and instead recognize the overall quality of the player.
Do you have a guild problem that you just can't seem to resolve? Have a guild issue that you'd like to discuss? Every week, Karen Bryan takes on reader questions about guild management right here in The Guild Counsel column. She'll offer advice, give practical tips, and even provide a shoulder to lean on for those who are taking up the challenging task of running a guild.