Precisely why I suggest it should be personal only at least for now. Once people come round the benefits of it and realise that hey, it's not automatically going to turn expert into a war zone then perhaps some form of group parsing for premades and such could be considered.
Whilst this is something I'd absolutely love, realistically, I think Yoshida would be more likely to go with a better take on the SSS concept, I made a fairly big post about this a year or so back. The gist of it was to have a DPS dummy mini game in the Gold Saucer akin to SSS but that actually threw mechanics at you (with the idea that failing these would stun you rather than hurt you ofc). That would be a more palatable first step, no ones going to complain about more stuff in the gold saucer and unlike SSS, it'll actually have an incentive for people to play about with it.
http://forum.square-enix.com/ffxiv/t...parser-problem
Looking back it, rather than figuring out a weighted scale for player DPS vs iLvl, a simple Potency per Second rating for each class would be a much easier way of scoring this whilst also keeping the regular DPS visible so people can feel the effects of their gear upgrades over time.