This system is already in place in another super popular mmo that I won't name. So, while the community in that game is arguably much worse than in this game, it is a system that is working fine for them.

The way it works in practice is not much different than the claiming system we have now. When you talk about unwanted help, yes it is possible, but since there is no benefit to helping a random player, you will still see players continue to ignore others and go about there business. Nice players may drop thou a cure if they see you in trouble, but they do that anyways.

tldr;

I don't think new claiming system will change the way players interact with each other in the field very much.