In this thread about dual-spec, one poster makes the common claim that certain mechanics are "crutches" which weaken guilds who use them. Rhaina posts a beautiful response that struck me as being so perfectly right that I took the liberty of reposting it here:
If you lack one leg, a a pair of crutches is an indispensable possession that allows you to move about in the world.
If you have two perfectly good legs, a crutch is unnecessary.
If you have two perfectly good legs, but you injured one, a crutch can be a temporary necessity. Eventually, you don't need it anymore. In my experience, the physical therapist thinks I don't need it before I do. In my brother's experience, the physical therapist is trying desperately to get him to keep using it for a week longer than he thinks he needs to.
I don't think it's at all reasonable for a person who can walk without a crutch to sneer at the one-legged person for whom the crutch is mobility and independence.
There are raids where intentional use of dual speccs makes the raid capable of meetings its specific goals. There are raids where relying on dual speccs is unnecessary and just causes angst for no good reason, and may even make the raid less capable overall.
Unfortunately, we can all look at the one-legged person and see that a crutch is a boon to her. We're not so good at just looking at a person who has two legs and knowing who will benefit from the crutch and who just weakens himself by using it.