Encounters are being designed so that no one single class is necessary, although the 25-man Razuvious fight currently requires at least one priest, preferably two or three, with at least one specced shadow.
Classes are being designed so that many necessary buffs, such as Replenishment, can be acquired through a variety of classes, rather than just one.
The rigidity that came with Sunwell is one of the reasons that development has taken this direction. The motto sparked high hopes, and not all players are convinced that the implementation has been successful.
In response, Ghostcrawler points out that just like everything in WoW, it is a process. It's not going to be perfect, because things are always changing.
In fact, the development teams learn a lot about class balance by watching us play the content. GC mentions that they expect Ulduar, specifically in heroic mode, "to shine a much harsher light on class balance."
This equates to admitting that they do not intent for content to be perfect on first release. It should work bug-free, ideally, and be balanced fairly well, but new raid content liek Ulduar is also an opportunity for study.
GC expects "great debates" about the necessity of various buffs, debuffs, classes and specs, and while it will be "interesting, perhaps a bit rocky...we're also prepared to make whatever changes we need to make."
I don't know about you, but this has renewed my excitement for patch 3.1 and Ulduar's release. This sounds tough, challenging, and our own performances will directly affect class balance and raid composition.
On the bright side, Ghostcrawler confirms that there is no current trend where certain classes are being shunned out of raid slots, and that classes that used to be ignored by raid leaders in BC are now working competitively alongside their raidmates.
Finally, he reminds us that the motto "does not mean class is irrelevant." What it does allow for is increased flexibility and creativity. Raid composition shouldn't be an exact science.
Patch 3.1 brings us Ulduar, dual specs, significant changes to all the classes, and more! We've got you covered from top to bottom with our Guide to Patch 3.1.