@OP: Maybe you are playing with the wrong people. My linkshell and I always have archers in our party. In fact we've done the speed run many times with several archers in the party. Whoever is telling you archers are no good just don't know how to play archer. We've actually beat ifrit several times with just about every class in the party. And as far as sentinel goes, it isn't necessary, but it certainly makes things go a lot smoother. But then again, that is one of the main reasons I enjoy this game, because you can utilize abilities from other classes (although class uniqueness still needs adjustments, clearly). But all in all, if you aren't happy with the game because nobody will let you go on the classes you like, then maybe you should create your own LS and lead your own runs and show people it's possible, I know my LS does.