Let's assume we can divide the player-base into three parts. On one end, we have the hardcores. I define them as players logging on every day. It doesn't matter if you're not actually raiding or doing arenas or anything, you just log on every day to do whatever you like to do in WoW.
On the other end of the scale, we have the very casuals, who just log now and then. They don't spend much off their time when they're not logged on thinking about WoW. They might be pure RPers, or just level alts (or mains) very slowly. They have no goals such as "become level 80, down a specific boss, obtain a specific item".
On the middle end, you have the group of moderate casuals. They log on regularly, but not every day. They have goals, and might even raid. However, they have a measure of control over their game-time and are generally not addicts.
Enter the daily heroicI belong mostly in the last group, the moderate casuals. At least used to. Okay, I've always had a lot of playtime on release of new content, but generally. Now I'm feeling I belong more in the first group. Why? Because I feel I lose something if I don't log on every day to do the daily heroic random. Somehow, it's gotten worse in patch 3.3. In 3.2, I knew that whatever gear I acquired with Emblems of Triumph were much easier to get in 3.3, and it was a lot of places dropping them. VoA, Onyxia, Trial of the Champion...
I like doing the daily random heroic, but I don't like the fact that I feel forced to play every day. The "forcing" is of course all in my own mind. It feels like it's pushing me further into WoW-addiction.