To me, it feels like;
- there was a transition from 1.x to 2.0 keeping some of the familiar with class combinations dovetailing into certain jobs
- 2.x to jumping straight into jobs in 3.0 with MCH, DRK and AST
- 3.x into 4 we do away with multiple classes to qualify for a job, classes are really not needed at all now.
Jobs are now advanced versions of the initial class, making class more of a tutorial into the job which you qualify for at lvl 30. Removing the multiple class requirements made cross class skills pointless, but role skills means that everyone in their role has access to the same basic tools of the trade. It feels to me like this was always on the cards from the start, but they did it slowly,
perhaps so that they could initially keep some of the trappings of FFXIV 1.x?