If you just all of a sudden starting using a parser, aside from your own data it's not that useful. But the more you have it running and looking at what everyone is doing, the more useful it becomes as continued use helps gain context and comparisons. For instance, you'll be able to tell if your DRG replacement for the day is trending behind your normal DRG by the time the first jump happens in A1, or if someone else on your team is just having an off run. You will be able to tell at what point healer’s dps starts to drop, maybe to time your own Virus or Eye for an Eye use next time to give the healers and extra GCD or two to dps. To be honest, the usefulness is near endless and limited only by the mind and creativity of the user. It really is great data that can be used in so many good ways. Playing as an Astrologian for instance, it helps to know who to give buffs to even in a PUG, or what dps to raise first if both happen to be dead. It's never the be all end all, maybe you want to get the SMN up first for another raise...or give the Balance to someone who just put up Raging Strikes regardless if they seemed to be the strongest dps or not - but it's a data point to help you along in your decision making progress.

To be honest, at this point I really think you are arguing for the sake of arguing. Your core belief is simply that it's a change that would create animosity from certain players to others. And that outweighs any potential usefulness in your mind.

My personal belief is that in a game where you are part of a group, everyone in the group should see how everyone in the group is doing, and DPS is important enough to be a measure. Then, we as players should best decide how to utilize the info, make decisions, and interact with each other.

I may never agree with you and you may never agree with me. That's ok - variety is the spice of life. But arguing that real time parse data isn't useful just seems silly - it most definitely is. I don't even think that's debatable. You just weigh your fear of player reactions more heavily.