If anyone in your alliance gets aggro by anything else, you can loose claim on any one of the mobs your alliance is currently fighting even if you still have lots of hate. Example: Go claim Fafnir/Nidhogg and halfway through it, stop attacking Faf/Nid, wait about 10 seconds and have someone sleep a darter. Wait a few seconds and Faf/Nid claim with turn unclaimed. If you are not constantly hitting a mob when you have multipule claims per alliance, you will start loosing claims on them. That's how people spamming on a mob get it from you. SE put that inplace so a group of people could not sleepga a huge area of mobs and kill them one at a time, keeping them from other people who want to kill them.
If you kite a HNM long enough, it will go unclaimed for a few seconds. You have to manage to survive the bezerk mode I talk about below though. It is one of the things SE made so people cannot kite a mob for hours just to make its spawn window during good JP, NA or EU times. JP's are known for doing it on Ramuh with Behemoth.
The other anti-kite-forever thing they did was add Bezerk or Super Sayian mode to HNM's. Take more than 30mins or so to kill the normal Behemoth .. you'll see what I mean

It becomes as strong as King Behemoth, if not stronger sometimes. Fafnir spike flail sucks already, ... watch it when he's powered up lol.