Did you come across this post and ask what's going on ?
I want to ask everyone in advance that I am absolutely not interested in a reply to this post along the lines of "No it won't work, they'll never add it to the game, I don't want it, etc".
If we let go of the negativity and look at the design issue holistically and together we can reach some consensus.
So what kind of RATING would that be ?
Some players in this game lack a reason to improve.
Yes it's about the style they play and there are methods from the developers themselves to help players improve on spell rotation for example.
Nothing against what has been there so far.
It's awesome and it works.
It still lacks a touch of motivation in my opinion.
So what is the motivation and will such a change hurt anyone ?
My suggestion if applied to the game would not hurt or harm anyone.
On the contrary.
It would just bring motivation to those who really want to be a little bit better or want to have some reason to improve.
In some other games (mostly older ones) after completing a level,instance whether it is a dungeon,raid or training mission after completing a player is graded with a scale ...whether it is for the best completion threshold marked with an S or a grade calculated in numbers like it is for example in the PoTD leaderboard.
How about applying a similar way of rating what a person really deserves and implement in the game absolutely to all instances in the duty finder and so on something like a leaderboard and then reward the player with a message "you were better than say 30% of the players, keep it up!"
Such a message would only be seen on the player's screen and would be calculated for the player.
A very similar system is for example in League of Legends (MOBA) where levels can be achieved with each character and then the player sees how much percentage they have improved by against others.
From time to time he gets a report that he has improved for that season.
I'm not saying that this exact system as it is in this game could be implemented in Final Fantasy XIV but let's develop a little imagination into the design and improve it.
Thank you to everyone contributing to the comments for trying to improve this idea or if they disagree with this idea simply and simply leave the topic and leave a negative opinion that doesn't move the idea/consideration forward for themselves.