I really hate a couple of the bosses from old WoW raids. If my guild doesn't have a dungeon or event or something, I go and do old raids (its good if you're into Transmogs, you want materials or just want loot). But what people don't know is that several raid bosses in WoW have triggers at certain levels of health and if those aren't triggered (usually by being stupidly overpowered for the raid), well the whole thing is borked and I've lost time, the possibility of rare loot and I'm locked out of the raid for a week.
Jerks