That was a great addition to your series (of which I think I've watched every episode). I'm a raid leader of what I call a casual 25-man raid group. We meet twice a week for only 2 hours each (we have members in EST and PST who work). I've been hoping you'd give your take on this topic and I think you covered much of the basics.
One thing I want to mention is that your definition of casual works pretty good, but I think that one thing that has allowed our group to continue to be somewhat successful, is that we have a subset (myself included) who don't meet your definition. I frequently work my life around the raid (for better or worse) but I do have to try to understand that not everybody can. Our biggest struggle is finding enough players who are comfortable with the casual schedule and the progression that brings, while still being capable players. Our attendance rises and falls frequently and it's likely the biggest source of my frustration.
I often think that I would rather consider our raid as a serious raid with a casual schedule. I've seen others who are successful with this, though none with only 4 hours of raid time a week. Any thoughts on what can make such a group work?