Unfortunately there are quite frequently classes with real, significant differences in their performance, and in high risk:reward situations, they can easily be the difference between making an encounter easy or nearly impossible. Goal-driven players will be seeking efficient routes to victory as a part of the challenge of the game, including the identification of "superior" classes and configurations.
Goal-driven players are also just as likely to form a reliable static party with their friends, and win with the jobs available to them. In fact, that's what happens in most linkshells, as shell members work together to get everyone through certain fights and missions.
I'm a believer that some jobs should always perform better in certain situations. It makes sense. Different jobs have different strengths, different mobs have different weaknesses. Different weapons have different stats. Different weapon types have different speeds. Different abilities do different things. Etc.
The hardcore players may get headaches over not having the job that does the absolute maximum damage per specific situation, but meanwhile, most gamers are simply happy to have jobs capable of getting the job done. And in FFXI, most jobs were capable of getting the job done in most situations.
EDIT: In addition, FFXI and FFXIV are built so that players can level several jobs, enhancing their usefulness in different scenarios. The leveling curve of FFXIV is shaping up to be way, way easier than the leveling of a character in FFXI. In other words, the people who'd get upset over having a job that's "not useful" will easily be able to level up other jobs to give themselves that feeling of usefulness that they need.
Edited, Mar 6th 2013 1:46pm by Thayos
Most linkshells full of goal-driven players are not "groups of friends" but rather people who can more or less get along and have similar player goals. As a result, they tend to feel very comfortable excluding people who are not useful towards their goal.
That aside, I agree with most of what you said, although I guess I disagree with your conclusion. It's fine and to a degree inevitable to have a balance which depends upon "matchups." i.e., situationally useful classes/characters. They exist in most strategy and PvP games. However, that matchup balance has to be balanced as well, and in XI, it wasn't. That wasn't something charming about the game--it was a pain in the *** that led to a lot of resentment, and generally, players not having fun.
FFXI wasn't a good example of class balance even considering matchup balance. There were classes which were generally useless, and they weren't well distributed across encounter types. A 25% difference in performance between classes is fine; a 500% difference is not.