If the spawn of a particular spawn is insufficient, I think (just my humble opinion) it's selfish for someone to tag/aggro all mobs around so "they" have a nice swarm while the rest around are left with basically nothing. If it's one mob ahead then I understand it (tag next mob so it arrives at about time when first one dies), but having more than two mobs on you, and wanting to keep them by yourself, is just selfish.
This is for mobs that you "claim", not extra mobs that you haven't tagged (deliberately); I mean, if I start to hunt feffs and I suddnetly get 5 big mobs around me, I wouldn't mind if someone takes one of two of them off my back, as long as I haven't started to shoot on it. I'm usually shooting at *one* of them and the one I'm shooting at I want to keep for myself. If feffs start to go rare though and I tag every feff on radar to be able to melee them (while radar is full of green dots looking for mobs), *that* would be selfish.
Maybe the core of the problem is that the spawn is simply too thin so that people start to fight for it, and the solution would be to increase the spawn. (As I don't hunt leviathan myself, I leave the support-ticket-writing to the people who do hunt leviathan.)