What exactly are you basing this on? I only have my own experience, but at least in the parties me and my friends are doing for learning and practicing extreme or Savage content (have been running Savage learning / first clear parties for 3 weeks in a row now for the floors we have on farm, taking newbies with us), we don't care about anyone's DPS before the group has met enrage several times. At that point, if someone is underperforming enough that they're personally preventing the group from winning, the situation will be discussed. If it turns out the person can't improve enough to be able to clear at that point, they will of course get replaced (so that everyone else wouldn't miss their clear just because of 1 person), but it's done in a friendly manner (they are encouraged to get some more practice and then they can clear for sure).
I have been running with someone parsing in a group since at least 2.0 (I don't remember if there were parsers in 1.0) and people have always offered advice first and given people a chance to improve, and only replacing the person if the person is really holding the group back and is unable to do the content at that time. And I definitely don't see anything wrong with that either.
(Now it's a different situation if a person is joining for example farm groups that only allow people who actually have the fight on farm. In that case, if there's a person who is significantly underperforming (as in if everyone would play at the same level they would never beat the fight), they may just be kicked instead of offered advice, since they intentionally joined a group and weren't able to offer what was required.)
More importantly: the parsers are already there, widely used (like said, it's pretty sure at least one person is parsing for every single extreme / savage run you do, practice or farm). All the things that can possibly follow from players parsing are already happening. Providing players with an official parser will only do two things: make it transparent (and, as such, fair for everyone included) and let PS4 have access to a tool PC users are already using.