I've played every class up through at least 30 (priests excepted, but I'm working on it) for this very reason. I know that's not the same as playing on a 70, but it does at least give a feel for what the bread and butter abilities of a class can do. I wish the game rewarded heavy alt players more than it does. We'd probably see less cross-class bickering if it did.

Reward heavy alt players... like account based attunement?
That'd be cool!

I've also tried to play each class... alas my Warlock & Shaman are level 10. But it does give you a chance to get a feel for them even if its very rudimentary its better than nothing at all.

I also don't specifically read blogs and forums about those classes (I stick to reading about Healing (Paladin & Priest) and Mages) but I will read whatever is written about here at wowinsider just for a general look at what each class is upto.

wowwiki has a great series of articles on how classes can use their skills to work together in a group, and how to help in a group in general.