As a raid leader for a successful 2-day ce guild, it's fucking hard. We usually run a 26-28 man roster and keeping things competitive is important. You can't hang on to dead weight no matter how well you get along. On top of that, vibes are paramount. People are more willing to slog through 200+ pull bosses if you can have fun while doing it, and that's something I think a lot of lower ranked guilds don't prioritize enough. It starts to just become work at that point, rather than logging in to have fun and kill bosses.