I'm all for this however you could do it with the current party size of 8. In fact if they balanced it properly it would actually be a lot more challenging if it was limited to 8 as you can't just throw more healing/dps at it with more people.

As far as the casual vs hardcore bit goes around here, everyone except for a few "hardcores" actually wants a challenge. Those few others simply want needlessly stupid timesinks. Due to college and work some nights I only have a few hours to play so I would be classified as casual I suppose. The thing is, during those few hours I would absolutely love to be powering through some truly challenging content.