I've actually already encountered that with one of my previous guilds. We raided 2 days per week, 3 hours per day. We were not the very best, but still got spine and madness before the nerfs. And we actually were recruiting on wowprogress, obviously we stated 'casual' (even though we were top100 eu IIRC). Then a holy paladin applies without glyphs and with mining as one of his professions. When refused, he actually said 'but you said you were casual why do you have so high standards'.
Yeah. That's because of MLG PR0 kids who believe casual = bad/not committing that shit like that even happens.
I've been raiding 2-3 days 6-10 hours per week at most for the past few years, constantly having nice progress (not the very best in the world, but killing shit when it's actually challenging yet), and I've been surrounded by incredibly good people who knew their classes, played close to perfect, never whined or caused drama, yet had a friendly and casual attitude and logged in literally to raid and sometimes do some auctioning to have enough flasks/food and other raid-relevant stuff.
That's the perfect casual raiding that's more successful and pleasant than 99% of hardcore 6/7 5 hours a night hardcore players.