People (mainly developers) are relating casuals to players who want instant gratification. Which is not true. People who want instant gratification are people who want instant gratification no matter if they are casuals or hardcore.

I categorize myself as a casual due to my limited time frame for playing games, but even I feel like the game is lacking in challenge. "Challenge" does not have to be quantified by time. You can play something challenging within a 30 minute time frame or a 4 hour time frame. In real life whenever I have a minute, I pull up Sadoku on my cell phone and challenge myself for those several minutes. It's up to the developers to relate that kind of thinking to an MMORPG and innovate.