In my experience, you usually don’t mark players on a per role basis. Marking players is generally done due to:
—Mechanic pairings: Sophia EX had a mechanic where a tank/healer had to pair with a melee/ranged DPS respectively to resolve a mechanic. People would mark players with two of the same color marker to dictate the four pairs. UwU has a system of marking people that got the Titan gaols so that they could line up and daisy chain them (but was not used by every group like Sophia markers were).
—Orientation: sometimes players mark another player to help orient the party, or for a stack or follow mechanic.

It’s rare that you see people marking tanks X symbol, healers Y symbol, and DPS whatever other symbol just to denote their role. I’ve never seen markers used like that ever.

I think permanent markers like this would just be a big mess of screen clutter. There’s a reason a lot people abbreviate names or don’t have names outside of their party showing: to reduce clutter.