We've had a few rounds (3?) of job-specific gear up to this point- Artifact, Myth, and Esoterics gear. This thread is not about those gear sets.

Instead, I wonder why melee DPS gear sets are the only ones without any overlap when every other gear set can be used for at least 2 jobs.

Let's break it down:
Melee DPS - 3 sets, 3 jobs
Monk - Striking
Dragoon - Maiming
Ninja - Scouting

Tank - 1 set, 3 jobs
Dark Knight, Warrior, and Paladin - Fending

Ranged DPS - 2 sets, 4 jobs
Bard and Mechanist - Aiming
Summoner and Black Mage - Casting

Healer - 1 set, 3 jobs
White Mage, Scholar, and Astrologian - Healing

See the disparity? An example of issues this creates: I have a friend that has mained Bard since he started playing. Recently, his raid group decided they would benefit more from a Mechanist instead and he found out that he was even better in that role! Yet, if I tried to make a switch like that after a few weeks, I'd be out of luck.

If additional DPS jobs are added, won't this just get worse?