The biggest difference between serious raiding guilds and "casual" raiding guilds is how fast they move. Wiping a lot isn't so bad if you are also playing a lot. Playing the game is fun. Waiting is not fun. Sitting around for 15 minutes waiting for someone to explain the strategy again is not fun. Waiting 10 minutes for the afk stoner to wander back to his keyboard is not fun.
We just instituted a new convention in our raids: a scheduled 4 minute break every hour. It sounds anal, but it seems to really help. No more AFKs after every wipe as someone goes to the bathroom; everyone can go at the same time. And having a break every hour seems to help everyone's attitude, too. I know I enjoy the opportunity to stretch my legs a bit.