Not sure if anyone else has noticed this but if you're in a party, and your party leader zones out, you can no longer gain exp or claim mobs lol.
My leader left the zone and everytime I tried to attack something the mob name would stay yellow and when it died I'd get no exp. Normally I'd assume it's a bug.. why would they do something like this? but then I tried it again and remade the group thinking it would "fix" the bug and I noticed that it actually gives you a warning when the leader leaves the zone..
A system error came up saying something like "the leader is no longer in the zone, you will not be able to gain experience points" something along those lines..