1 thing needs addressing or altering that I can see, that being the NM's which need doing anyway imo.
Static spawn elite mobs are a weak content source at best, they could with a little effort be a lot more engaging and fun.
My other comments were to add more types of content.

But I can't agree that it would be a free for all, in almost all mmos most people can help others or leave others to what they doing, i doubt that would be any different here.
I don't want FFXIV to be just another mainstream MMO, but a mob becoming immune to all attacks from anyone but the person/group who tag it..
It lacks immersion, depth and it adds nothing to the game, other then isolating people more.
For the amount of times someone would get involved unwanted, I can hardly see it causing issues.