Balance, Homogenisation and Encounter Design: The Problem.

[Ladon]

You can’t design encounters and job mechanics to high specifics when you are capping party sizes to 8. This is the fundamental reason they have to make sure every job in a role can do the same thing and that no encounter requires specific skills from specific jobs.

The only way you are going to see old style class systems is if the entire game is built non-instanced with non-capped player encounters that allows for loose class compositions.