The difference between here and XI is the fact that magic classes like BLM and SMN had the tools to actually heal in a somewhat effective manner in XI thanks to Cure Potency equipment in the pre-Healing Skill update (not so much now that Healing Skill has such a huge bearing on how potent your Cures are in the XI universe).

There will be times where a heal from a DPS class at a critical time will prevent a wipe, but those opportunities should be few and far in between. It's not to say that a player should not be adaptable during this time, but it certainly isn't their primary purpose as a 200 heal shouldn't be that game breaking in the grand scheme of things of the end game. These situation arise more often in early game dungeons when any class with a heal can effectively heal any Duty Finder instance.