Ironically, I was working on a post with a similar premise, but was trying to figure out a way of organizing it. I can post a snippet here regarding some of the criteria I came up with

Basic Requirements:
All Jobs:
● Anything integral to the jobs/roles identity should be acquired by or before level 15 (by this I mean things like core role actions, Tank Stance, Pets for SMN/SCH, Greased Lightning, Astral Fire/Umbral Ice, Dualcast, Dances, etc)
● Any gimmicks that are unique to that job should be introduced between level 30-50 (by this I mean what the Job will be known for. It might align with their identity from 1-15 of be more unique. Things like AST cards/sects, Regens on WHM, Shields on SCH, Mudras, Jumps, Sen, Songs, Heat Gauge/Turret, etc)
● A rotation that slowly upgrades as you hit each level cap, and doesn't make you feel "gated" for not being at a level cap. (Basically, the job should feel complete at level 50, and get progressively "better" with each level cap. The new MCH is a perfect example of this as it feels complete starting at level 50)

To add to this but not go into too much detail, each job/role should have certain abilities at certain level ranges. These abilities don't need to be a 1:1 ratio, but should function similarly. Case in point, at level 15 SCH is the only healer without an AoE heal. Simply shifting Whispering Dawn to level 15 would fix that issue. Granted, Sastasha is the only dungeon where this skill isn't available, but it's still odd. Additionally, having certain skills at some levels make no sense. You can use Diurnal Sect at level 30, but it doesn't "do anything" until level 34.

Reshuffling some skills so they make more sense would be a great thing.