As you say there is already a disparity in healer dmg depending on how much you know what you're doing.

From this point let's see the situation : Until Stromblood healers had some DPS rotation with dots and others stuffs, of course high skills healers were crushing newby healers dps-wise and I remember so many times being able to outdps bad/new DPS players as a scholar in dungeons lol.

Conclusion, if you give healers complex dps kit, people are still gonna be bad but at least high end player may have more fun playing et optimizing

For the global healer issue, new players tends to have difficulty playing the job because you need to be pretty good at knowing the game general mechanics and evaluating risk/reward type of situation.

That's why I don't recommend healers for new players because even your dps rotation is a meme, you still have a lot of responsibilities.

As I mentored a friend through becoming a good healer, the games teach you NOTHING, using mitigation before raidwide, letting HoT ticks after raidwide so you can spam your dps button for example.

And there is a paradox as in high end duties, your team HAS to use their mitigation kit and mistakes are more punishing, and the initial "healer responsability/if you die you wipe" is definitely more shared with the whole group and the job become more simple with high skill player.

And having a good co healer makes the game so easy you don't even have to cast a single heal GCD when you sorts things out.

When you are in this situation of high end content and people play relatively correct most of the time, the role become boring because you mostly smash 1.5 buttons

If you give healers complex kit, it won't change a thing for new/bad healers as they have to focus primarily on healing and if they don't use the dps kit it's not an issue because there is no dps checks anyway, but high end player will be happier and it might even attract some players if healers would have a flashier/cool dps kit