The A-B-C quest is a common, likely the most common, plot structure in high fantasy (not so much in sword & sorcery - still not the same thing), but it's not the only one, so calling it a necessity might be pushing it a little. Does make sense as the default structure to focus on though.In swords and sorcery, quests are a necessity.
Overall a pretty solid column this week. Good advice on writing quests and prophecies. It's nice to have the real Steven Forbes back.