Regarding the issue of MPK during battles with mobs that have highly desirable drops, (serket, simurgh, kirin, etc.) perhaps the issue could be solved by only allowing interaction between players with the same linkshell equipped.
Ie: A fight vs Jormungand requires a great deal more than 18ppl to succeed.. There are going to be additional melee building TP for WS/SC, combat mages resting for MP, healers healing the main combat alliance, even additional parties/alliances to handle other mobs that may spawn and interfere with the battle, etc... All of which are the commonly used and logical actions for 90%+ of those successful.
As the system is now, a 2nd non-related group of players could train in a bunch of mobs into the area the fight vs the Wyrm is occurring in, purposefully lose hate by whatever means, allowing "their" mobs to wreak havoc on those involved in the fight against the wyrm.
Or, that 2nd group could focus on exploiting the "loss of claim" bug that occurs frequently for short periods of time during long battles, in an attempt to outright steal the contested mob, often when the mob has been reduced to a pathetic state by the legitimate players, resulting in an easy kill and theft of the dropped items.
There are other means of MPK/griefing, but I feel that these could be the simplest to fix.. That's right, simple to fix.
Suggested Fix: Limit the interactions of those involved in a fight against any NM to those equipped with the same linkshell. ^^
This would not alter the current combat system much at all, except effectively putting a linkshell-limited /blockaid up on all members in the same immediate area (longbow/casting range basically) as the NM that is being fought.
Fix #2: Eliminate the "loss of claim" bug that occurs during these longer battles when a player with the NM's attention dies/DCs/disengages (or warps/teles/zones for that matter.) I personally like the suggestion that as long as anyone on a NM's hatelist lives, it stays claimed.. This would also insure that the big NMs that necessitate multi-alliance battles are not futile efforts, with the same group that started the fight retaining claim until every member is dead/zoned..
It seems truly unfair for a group not involved with the wearing down of an impossibly difficult NM to end up grabbing the claim, kill, and loot due to this.
Fix #3: Somewhat related to #2, eliminate the same "loss of claim" effect for BST due to their pets. It does not seem unfair to me for a BST to use the tactic of killing 2 mobs at the same time with a strong pet, but it is unfair for other players to exploit the bug at this time to steal the claim of any of that BST's targets.. I believe this is also what causes some BST to become bitter and willing to MPK others for little reason. Eliminating this problem could reduce the issue of BST MPK'ing to a non-issue. ^^
Fix #4: Please increase the spawn rate of normal NMs that only drop R/Ex equips! >_< For instance, if Argus was a 30min pop, then the competition on it would rapidly fade. Worries of MPK'ing would evaporate as well.. This should be done on all the lower level NMs that drop the lower lvl equipment (40 or lower) that are considered "end-game" equips... Peacock Charm, Leaping Boots, Archer's Ring are all very good examples of this... and while the recent changes to alternate, yet identical, R/Ex drops was a smart move, there needs to also be an increase in both the spawn times and drop rates of these kinds of equips... Having to camp Leaping Lizzy for days, getting many claims and kills, but not getting the drop is a frustrating experience, both for the veteran who is looking to get "the best" equipment, and the newer player who wants "the best at my level" equipment but has to compete for the claim with the veteran.. when no one gets the item, no one is happy.. Also, regarding this type of issue, please consider making all 21-24hr NMs have a 100% droprate of R/Ex equips... ^^;;; It is unbelievably frustrating to spend days and weeks of available game time repeatedly camping/killing a NM that only drops a R/Ex equip, but not getting the drop... I'm sure that if they were 100%, there would even be more players willing to help each other out, while now, they shrug off help requests due to them most likely being a pure waste of time.