There is one viewpoint here (and it's not one that I necessarily espouse) that HC is just falling into the old "hardcore/casual" trap that Penny Arcade put so well this week -- he thinks that he's casual, when actually, if you're running higher-level-than-you're-meant-to five man instances with your friends (and theorycrafting a bit), you're actually what Blizzard would consider a hardcore player, and thus of course the game is easy for you. But while I think there's a little bit of that going on here, I don't think we need to go that far: the fact is that WoW is an easy game. That's how it's garnered such a big audience. And anyone who has ever beaten Diablo is going to find that yes, if you read a guide or two, run the right instances at the right times, and put some thought into your specs, you'll have an easy time.
So what HC asks for is the difficulty to scale -- instead of just Normal and Heroic, have three or four modes that players can choose to set their own experience. A few games have done this already, and indeed, Blizzard may decide that that's called for in future instances (though it seems unlikely that they'll do this on older content, considering how they've abandoned it so far). But for now, WoW is an easy game, and that's the way Blizzard wants it. After all, you don't get a 10 million subscriber base by beating players up.