Why can't a monster stay claimed until it kills anyone that took action on it and goes idle for a certain amount of time?
And if you want to unclaim a mob without dying? Your just sol?

Here's one of several typical scenarios of how claim gets lost:

1) Fighting a monster.
2) Main tank starts to disconnect, can't move away from the monster, can't move the monster.
3) One of two things happen here:
>> a) The tank is forced out of the game and the monster goes unclaimed.
>> b) The tank is forced out of the game, the monster goes unclaimed and all party members are forced to disengage because the current coding makes the disconnecting member drop party before they drop off the server....
4) Sociopathic player/group takes advantage of this and claims the monster, kills it.
So you pull hate off the tank, move the mob away from him, and then attack it, so he does not have claim.

It really is not hard to keep claim on mobs, regardless of what happens.

The only "faulty mechanic" here is charm. Everything else works as intended.