The problem with the system in FFXI was not the system it used but the people that expected you to use it to achieve an optimal build and that will be no different in FFXIV. As soon as a skill comes out that is as effective as Utsusami then it doesn't matter what class or rank it is people will expect you to have it, especially if you are a tank.
The game at the minute provides little challenge for people to have a reason to have these optimal builds but as soon as they ramp up the challenge and certain skill's and abilities start to shine through then people will start expecting it.
The current system is not so flexible to allow you to really make any class you want like some seem to think, if I invite a GLA to a party I would expect him to tank, if he turned up and said "no I want to main heal" then lets just say that wouldn't go down to well. If I invite an Archer he will be a ranged attacker, if I want someone to main heal I will invite a CON or THM.
The only thing the current system does is help with building a solo class, so you can add those cure's and defence moves to make it easier. I personally believe it would have been better if they kept the sub job system and allowed you to call your companion to help you solo. So if you were a DD then your companion could be a mage to help cure, if you were a mage your companion could be a tank or DD and so on.
By doing what they have done it will create a balancing nightmare and as such they will really struggle to make classes unique as if they give them something good, then unless it is tied to that class people will expect you to have it on your class.