Hmm I played on Pandemonium when i was doing the XI thing and it was pretty much understood by everyone that you grab for the NM when it pops, dibs to the winner. Least that's how I remember it. I remember camping things and fighting for claim all the time and that was the norm.

I was pleasantly surprised when I realized people (most of the time) try and work together or take turns in XIV. I've had people do things like this to me and while I was annoyed at the moment I always try and think back to XI and claiming against others. One one hand it is polite to wait your turn or work together, but on the other hand there is only one of that mob and plenty of players that want to get at it. It seems natural that there would be competition for the mob sometimes. Those same people that are taking your mob worked hard to get a party or get to that spot and want to claim it as badly as you.