As we've suggested a few times, we are currently taking a serious look at all of the various buffs and debuffs classes can bring to parties and especially raids. A few of these changes have shown up in the recent build, and more are on the way. I'll first explain why we're doing this and then what generally we are doing.

Why we think this change is necessary:

1) We are adding a new class in Wrath of the Lich King as well as improving some specs that were previously viewed as inferior for PvE. Yet because the raid size is remaining at 25-players (and we expect many people with raid with 10), it may be hard to fit more people into your raid.
2) We are moving almost every buff to affect the entire raid. There are only a few exceptions, and these tend to be short-term, bursty abilities. Most buffs from Battle Shout to Leader of the Pack will affect the raid.
3) While we are likely to increase the debuff limit on bosses, this is a problem we keep running into. Furthermore, it asks a lot of players to be able to parse bosses with 30, 50, 100 debuffs on them. At some point, we need to stop the madness.
4) Stacking a raid in order to get the right buffs has started to feel a little like a crutch, much like stacking consumables felt not so long ago. Because some of the buffs scale so well and have so much synergy with other classes, you may sometimes feel that you should pass over a really skilled player in order to pick up a buff that will bring more to you group. We'd rather get back to bringing good players or, gasp, even your friends.
5) We want the challenge of the encounter to be the fight itself, not collecting all of the buffs and debuffs you need to succeed. Buffs are fun. We don't want to cut them or nerf them significantly. But we do want to make benefiting from them less of a burden.

Some changes you're going to see:

1) Ease and flexibility in getting all of the major buffs in the group, while still having a few spare slots to take the people you want to take.
2) More parity in which classes can raid. While it's probably not realistic to get 2.5 of every class in a 25-player raid, we can get a lot closer than we are today.
3) More overlap in buffs and debuffs and very few unique buffs. If you can't get player X to bring the melee haste buff, maybe you can get player Y.
4) No two classes should have the same set of buffs. This is to make sure that one class can't completely replace another. If you have two players both bringing melee haste, there is a good chance one of them also brings something else you need. Again, the goal is flexibility.

A few examples:

1) To get a spell damage vulnerability debuff on a boss, you can bring a a warlock for Curse of Elements or a death knight for Ebon Plague. They don't stack, but both classes also bring additional benefits in case you want to run with both. The lock brings Curse of Recklesness, Demonic Pact, Curse of Weakness, Blood Pact and Fel Intelligence (depending on spec). The death knight brings Abomination's Might, Improved Icy Talons, various Auras, and a new Str + Agi buff you haven't seen yet (again depending on spec).
2) To get a 5% melee crit bonus, you can bring a Feral druid for Leader of the Pack or a Fury warrior for Rampage.
3) While having a mana battery feels essential in many cases, you can now bring a Shadow priest, Retribution paladin or Survival hunter to fill the role.
4) You can improve health of the entire raid with Commanding Shout or Blood Pact. You don't need both, so perhaps the warrior can Battle Shout or the lock can bring out another pet instead.

I want to stress that none of this is set in stone. A change like this is going to take some iteration until it feels right. While we are pretty happy with the plan, it is certainly possible that some class or spec is going to be hurt by a change more than we anticipated. We don't want to hurt anyone's viability while soloing, in small groups, or in PvP with this change. We aren't trying to slap anyone in the face -- we're trying to make the game more fun.

The goal is to get more people into raids and to let you bring the people you want. Ultimately, that should benefit everyone. Please try and keep that in mind as you start to see the changes.

And of course, please share your feedback on them with us.

The goal is to try and boost Affliction, and any other spec that has been traditionally under-represented. We haven't made much of a numbers pass on classes yet -- we're still in the stage of building new talent trees.

Without getting into too many specific examples, the 5 warlock stacking for Sunwell is exactly the kind of thing we'd like to avoid. Warlock 1 boosts Shadow damage, so warlock 2 does more damage, and warlock 3 does damage and... hey why did we bring a mage, we'd do more dps with another lock!

If I need to come right out and say it, stacking a class for a single ability such as Bloodlust to be used in rotations is not good for the raiding game. I think most players suspect as much.

I'm not so certain raids will fill their remaining slots with rogues and hunters. For one, those classes aren't going to be taking a lot of advantage of all those nice spell buffs you've got going in the raid. Two, if they are bringing buffs, it isn't fair that their dps is greatly superior to everyone else. Higher dps is fine, especially for classes that don't have the option to respec into tank or healing. But it needs to be a modest dps boost, the kind of thing that will be swallowed up by variance in player skill for all but the absolute best 1% of raiding guilds.

Now we're not [very] naive. We know you guys are smart and will come up with ways to min / max a raid. But we're hoping this change will reign in that in to some degree. Even today not every Sunwell raid is stacked the same way, and with more flexibility on who is bringing the buffs, raids should be even more diverse going forward.

It isn't our intention to dumb down the game. In fact, we want the challenge to be more about the encounter itself and not the buffs. When you think about it, it's not a big mystery what buffs you need for a good raid. The challenge is in finding good people who can fill those roles while explaining to good players that you just can't use them tonight. That's a logistical challenge I guess, but we are making the assumption that most players would rather face strategic or tactical challenges. In a game as large as WoW there will be exceptions of course. We view this similarly to actions we took when raids ran around getting the Zul'Gurub or Onyxia buffs before going on a raid. That wasn't particularly fun, but people felt like they had to do it or they'd be surrendering a big potential advantage. The flask stacking and consumable stacking got to be a similar burden. I'm not sure a lot of people wish for those days again, but no doubt some do.