If you want to reach the maximum potential of your class, sure, there are number crunchers out there who will tell you the best talent and stat choices to make, spell/ability rotations, etc. But the information you need to be successful in your role is really all in the game. We've gone to great lengths to ensure things are clear enough that you can make some meaningful choices for your character's power on your own, and still have a great shot at catching onto what makes you excel.
If you're speaking at all about boss encounters, I think you'll dig the Dungeon Journal (formerly referred to as Encounter Journal) coming in patch 4.2. Once we're able to catalog more of our dungeons in this journal, you'll get a lot of essential information for each boss fight. It's not going to tell you how to beat the fight, but it's going to tell you what kind of abilities the boss will be using against you. You'll just have to figure out with your party or raid how to deal with those abilities when they're used. Dungeon Journal will also help you find the loot you're looking for from each boss ahead of time, so you have items in mind you hope to get before even setting foot in the dungeon.
Why do people just dismiss others by saying "look it up on wowhead/mmo-champion/wowwiki/elitest jerks/etc"? I've played many other MMOs before and they didn't need "research" as you people put it like WoW supposedly does. And they were still fun. Phantasy Star Online is still going on after 10 years without any expansions or updates and people still enjoy it and they don't need to research a bunch of stuff for encounters and so forth.
So please, I think we are going in the wrong direction if the pre-requisite to playing WoW is akin to studying for a test at uni.