People who have access to parsers and use them are generally not the bulk of a player base. The bulk of players are not clearing raid content under geared or even at average ilvl. I'm not saying that the information gleaned from a parser isn't valuable or that FF or any other game should try and keep people from using them. It's just that so often they become the end all be all even in situations where a high rank from a "proving ground" would be proof enough of ability. The problem is that the bulk of players look at the parser and see the monk doing 500dps while the black mage is doing 350dps and assume that the black mage is performing poorly. An experienced group will understand how to weigh the whole of the situation while most will condemn and ridicule and kick the player.
Because of this, I'm not proposing this solution as a replacement for parsers but as a way to give the majority of people a fair representation of themselves. There may still be things you can do that are fight specific to improve but if a player is reaching the upper end of a proving ground I can at least bring them into a pug group with more confidence that they will perform at a level that I need rather than going in completely blind and taking their word for it.