In an ilvl MMO system healer DPS is pretty much inevitable since Duty Finder content has to be balanced around the lowest ilvl to enter.

If they make content where people at max ilvl have to spam heals with no time for DPS then people entering at minimum ilvl will just get obliterated.

Unless they make ilvl synching to match the minimum ilvl of the dungeon it's only natural that as the party increases in ilvl the tanks take less damage, the healers heal for more, and the DPS kill stuff faster resulting in less time needed for healing which frees up more time for damage.