Several commenters advance the notion that looking up talent and gear optimizations is not fun.
And there's a lot of truth in that statement. Coming up with your own specs and strategies is a great deal of fun. Personally, if I'm looking at something new, I like to make up what I think the optimal spec will be and then go to Elitist Jerks and see how my spec differs from theirs and why.
But you know what isn't fun? Wiping.
It isn't fun to wipe to bosses you know that you could beat if only that hunter over there went to EJ, looked up a decent spec and rotation and tried it out. It isn't fun to watch your guild die because you stalled out at a boss that you know your team had the skill to beat, and optimal specs, gemming, and rotations would have been enough to push you over the hump.
I've been there and done that. To be honest, I've probably contributed to the problem in past guilds.
I'm in a guild now that takes it for granted that players will use the Internet to help determine optimum specs, rotation, reforging, and gear. That every player will come to raids pretty close to the accepted optimum for all those elements. If you app to us, and you differ from the optimum, you will face extra scrutiny.
And you know what? This is enormously freeing.
It takes so much of the "busywork" off the table. We still struggle with fights, but we're struggling with execution, and mastering the mechanics of the fight, not basic elements of how to play the class.
Talents, gear, and rotation are only the tip of the iceberg when it comes to playing. They're the basics. Using community resources like EJ allows you to "shortcut" past those basics and work on more advanced techniques1 and fight-specific mechanics.
Ironically, taking optimization for granted allows you to focus on playing the game, and not playing the spreadsheet. Someone else has made the spreadsheet for you, has done the math. Leverage their efforts, steal their results, and you get to focus on making the right gameplay decisions for the fight at hand.
1. For some examples of more advanced techniques, see Kripparian's video.