Those are my most recent failed attempts. They are not the first set either. Casual raiding guilds are damn hard to define. And that's precisely why I think so many fail to progress or even not collapse.
Guilds need common goals and expectations. Without these they're just a glorified chat channel. But so often casual raiding guilds fail to set these goals and expectations. Well, they might get the goal part in a generic or distant way, such as "raid" or "kill Arthas", but what's next week and how are we getting there? Expectations are the real killer. What gear should people have? DPS? How much attention should they pay? How about preparation: gems, enchants, consumables, strats?
The person who does more feels like the rest are dragging him down, while the people who do less may feel pushed too hard. These players can play together, but they need to know what they expect of each other and reach a compromise. More likely, they'll split away to other guilds or form useless cliques within the guild. Either way, the guild fails.
I'd define my current guild as casual. We raid a few nights for a few hours. No one is screaming on vent. No one rage quits. But we all sit down and kill internet dragons. We chat and joke and laugh, until we need vent clear to coordinate the killing of internet dragons. We're not amazing players and we're not terrible players. We're just people who expect each other to learn quickly, pay attention, and enjoy killing internet dragons. It's a friendly, helpful ass-kicking social guild.
9 hours ago