Well within the same class/role you would likely see people with the same gear like all Gladiator Tanks would have a set of gear but that's different from Pugilist Tanks. Similarly Pugilist Tank gear would be different from Pugilist DD gear. It's already kind of this way except you have a lot of the gear being shared between classes for similar roles, this is especially obvious with mages.

To achieve good diversification they'd have to break gear down from broad to specific, example:
Conjurer > Black Mage > Nuker > Water

You start off with the most broad gear, gear simply for Conjurer and then start getting more specific by selecting the job, role within the job and then a specific build for that role.

To do this for the Disciples of War they would have to make multiple builds within any role viable for the jobs. Like having Vitality builds and Dexterity builds be viable for tanking for all jobs. Gladiators/Paladins would use bigger heavier armor/bigger shields/bigger swords for Vitality builds but the lighter armor/smaller shields/shorter swords for a Dexterity build. I say Dexterity instead of Evasion simply because for something like Marauder Dexterity means Parry. Currently this isn't quite as possible but it should be looked into.