I will tell you as one of the wow designers, it is a very bad idea.
The ags designers i hope will understand the following points.
To sum up players in a single word, you’d use the word “efficient”. We can spend hours designing and developing content and they will ignore it for a single bugged spot that grants x% more xp (or more) just because it is more efficient.
It is this characteristic that drives the actions and atmosphere of mmos. If people are “deemed” less efficient, the result will be a negative, and toxic experience for them (being called various insults and kicked from group). This will bring about toxic less effective forms of social erosion (the point at which people stop doing things together).
Damage meters even if added to only track one’s own abilities would ultimately be used in similar ways by mandating screen shots at the end of various raids, dungeons, etc.
In fact, we had this discussion here tonight on discord, and one of my members brought up that people use the stats board at the end of wars and opr just for this reason. In some way, these score boards provide a temp-version of damage meters and its the way people are judging if a player is bad or good. IT may be that they just run a less popular, less optimal (but viable) build.
Lets take for example elysian/boba tee. In wars they generally damage twice that of others, yet in most cases they do not win the wars because they have not learnt the value of the other side of things (or just dont care). Yet, people judge them as better because of such numbers on the score board.
These sorts of mechanics (scoreboards, meters, etc) will ultimately cause more problems then people need, they provide no real benefit to the game, and cause a lot of toxic drama.
Might i add, drama that the game does not need right now.