The newly revealed 4.4 Tomestones of Genesis gear shows off interesting designs and fine aesthetics.
But not for healers and casters. In fact, for healers and casters, they mainly differ from the Diamond Sets in the design of the borders. Here's the healer Diamond robe.
A texture swap would not cause major differences.
Now look at the Ryumyaku and Genji healing body pieces.
While not as similar, they are still more similar than corresponding pieces from other jobs' gearsets (and it sticks out because the healer gearsets are often unattractive, especially on male characters), and tie down players to a narrower aesthetic range than any other role.
An overhaul of this pattern might be a fantasy (and this pattern seems to have gotten worse in the Stormblood endgame; stuff as adventurous as the Eikon Cloth Acton or the Serge set exists, but is a long time past). But cross-job (edit: I mean cross role) glamours would go a long way relieving the problem.