Seems to me that, as we get further and further into the game's life-cycle, and more and more content - including the most extreme - is being cleared without need of an official parser to do so, that the idea of one being necessary becomes less and less convincing, while the idea of one - for anything other than purely personal training/tracking purposes - seems more and more redundant.
The player base has proven, and continues to prove,that it doesn't need a DPS meter to complete content. To try and argue that it does is really pretty silly. It's a 'want', at best. It's definitely not a "need".
However, any such implementation should remain purely for personal information. A player should be able to see their own scores, with perhaps a comparison to the average or top numbers currently on record for any given content. This way, if the individual wishes to refer to that data for their own use... they can. If they wish to ignore it because they're doing just fine even without it (as we all have been since 2.0 launched, unofficial parsers notwithstanding).
If an individual wishes to share their parsed data, cool, they can. But it's their choice to make. The choice isn't made for them.
Making all people's parser data publicly viewable, for all others to see, especially in a group situation (across all content) is just asking for trouble. For people who are prone to being a-holes to everyone else already, you're just giving them more ammunition to do so with.
And let no one kid themselves... This does happen, and has happened, in every MMO to ever release, for well over a decade now. So long as there are people who have this "need" to divide the player base into "us against them", using any divisive means they can muster - and there many such people - you can guarantee they are going to be all over that should DPS stats be viewable to them.
Hell, even without that data, there are already people who will complain about others' performance, for nothing more than "this run is taking longer than it should" - even if bosses are being cleared, and no one's dying or running out of MP, etc. I've specifically had that happen in many of my parties... including pre-50 content. Giving these people actual numbers to work with is just pouring fuel into the fire.
Yoshi-P is aware of this. He knows how people in the MMO space can be. I believe that's why he's so reticent and guarded about implementing such a feature, and so cautious in how it's implemented. And he has the right of it.
So, implement a DPS meter that's entirely for private use, for private viewing and reference, and leave it at that. Many have argued it's solely for personal growth and improvement, so that's fine... leave it as such. Don't make such a thing publicly viewable.