In general, remove the 2 minute meta and spread out potency so DPS isn't so reliant on nukes critting in a 20 second window. Make buffs more varied beyond damage% up or crit/dh% up. Vary them in their cooldowns as well, giving options for aligning after downtime, but making it not optimal in a dummy fight.

Add 2 and 5 piece set bonuses to capstone level sets.

Then add a Specialty stat that enhances a job's niche and acts like a buildable passive (i.e. SCH Spec could enhance the effectiveness of Chain and Fairy skills, maybe give a buff to Catalyze for their crit shields).

For anyone who plays HSR:

Shield Healers = Preservation/Nihility
Pure Healers = Abundance/Harmony
Support DPS = Harmony/Nihility
Pure DPS = Hunt/Destruction/Erudition
Tanks = Preservation/Destruction

Accept that jobs won't be perfectly balanced and some may be more effective paired with others, and some may be more effective in specific fights.

And that is my job identity fanfiction.