The Holding Hands achievement during Hagara in Dragon Soul can be one of the most frustrating things for a 25-man raid to complete. Originally, we tried several times with a long snake-like path. We found the lightning would occasionally refuse to jump between some players, which seemed to fail the achievement when we maneuvered players closer to force a jump. Even if it works, the setup is time consuming and the raid has to survive extremely high damage.
Then we found videos of the achievement with a simple line of elbow-to-elbow players. Ridiculously simple, stupidly easy, and still not 100% reliable. It took 3 tries for us to complete the achievement twice.
It’s issues like this that remind me why I’ve never been much for the Meta mounts and achievements.