SE probably does not want to take any responsibility from the community complaining that a feature that they've made is hindering their progression with other players.

If it was implemented, the 'weak' players will get kicked continuously because of the DPS-meter and you'd see a serious uprising, but it would make it easier to form groups, picking the right players. At that point, SE would be siding with the hardcore players and suppressing the casual players.

For SE to remedy the situation would be to have new gear, difficulty changes, etc, to push the players DPS/heals/tanking capabilities further.

This is why we see later patches that will benefit the casual players to 'catch up' to the competitive players.

Right now, SE is in between casual/hardcore, leaving the rest of the matters (such as yours) in your hands, not theirs. This is the only reason why I do not see them implementing such feature ever.