World of Warcraft uses a TCP protocol (would post a link to the reverse engineered protocol information as proof, but Blizzard seem pretty aggressive at hunting such sites down so couldn't find it on Google :P)

So, where in your code would you put the delay in order to be sure that it won't cause the game to feel less responsive? Just after the rendering? How exactly will you determine the duration of the delay? How about timing accuracy? Sleep() on Windows is in milliseconds. And how will you deal with frame rendering time suddenly dropping or rising? I know it doesn't matter in the menus of Starcraft II, but I can promise you that some crazy Koreans will care a lot if Blizzard put an (unnecessary) Sleep() in their main loop. Of course this needs to be an option (which it is).

There's a difference between learning what does what and learning how to use every skill you have effectively. A lot of players fail at the first step, only learning what 5-6 skills they'll use the most and ignoring the rest. The result is Paladins who don't heal others, Warriors who tank in Berzerker Stance with a 2H, and Druids who aren't aware they're different from Rogues.

I also find it quite strange that people continuosly bash WoW for being so incredibly easy, and how everybody can learn to play it in a matter of minutes. How can it be then, that a very large percentage of random groups you do instances with, fail miserably because someone don't know how to play? Even if the instance run is successful, it could always have been done faster and more smooth. I think many people believe they play perfectly, even though that's not the case. And unfortunately most people are reluctant to point out these people's weaknesses - the most contructive criticism that usually comes accross is in the style of "OMG L2P noob, WTFBBQ!!? LOL LOL you suck!!1". Which of course not is taken seriously by anyone. And no, it's not just about having good gear. A player with good gear can still go total pew pew on some mobs, outaggroing the tank by miles, and maybe think he's the best player in the world because he's on the top of the damage meter. Etc, etc.