The point of the mentor system is to connect new players into the community, the idea is that people who are patient and willing to help will introduce new players to the game. At no point is it required for you to be the best at your class because that does not make you a good or bad mentor. The best mentor are the people who are patient and enjoy working with others even if it is slow/inefficient. To assume all new players want to be raid ready at 60 or raid at all is silly. Many will enjoy just exploring the world. If you want to be a mentor realize everyone one who starts playing might want something different and help guide them there. All in all it is up to the players to develop the community not the devs.