Proving Grounds is just a way to gauge if you are ready for raiding. It doesn't give you what a parser does. Being able to see your DPS during the actual content is invaluable as it allows you to tweak things on the fly. And every fight is different... buffs used at different times or saved for certain phases, different movement patterns, multi-DOTing, etc. FFlogs has been a great way to allow PC players to upload logs for their PS players to look at, but the API still needs to be finished.

WoW has Proving Grounds, but it's not just a gauge of your own ability. It's also a gate to keep bad players out of difficult PUG content until they improve. I'm not sure that's a good route for FF to go though. D: