I think the 'core raider' system is unnecessary and the cons outway the pros. Obviously decisions have to be made on who will be in the raid for each fight which is a balancing act between giving everyone an opportunity to play and making sure we down bosses and progress. But I really don't care that I'm labelled a 'core raider', and would prefer not to have the title given that there are others who feel lesser for not having it.
As for the casual/hardcore thing, I'm happy with what we do. We get a good amount done in the small time we have, In the past I have been in a 25 hour/week server first guild and there lots of players in our group who are just as good as the ones from that guild.
Thanks to the officers for all of their efforts in running raids, doing dkp, dealing with nonsense, etc. I appreciate it!