Did anyone ever think that when we don't see a mob it doesn't exist.
Sounds stupid, but if no-one is around; why should MA leave those mobs in RAM memory on server? they could just aswell dump it and recall it when someone is around. Some area's on calypso are devoided of player activity long enough to make the effort well worth it.
I guess there are 4 kinds of things:
Static parameters that never change (like dmg power and stamina/max HP)
Dynamic values that are saved for a mob (in his case current HP)
Dynamic values that are discarded
Dynamic values that change over time (HP and location - when someone sees mob)
Keeping values for a mob in the server probably doesn't take so much resources, all you need to keep track of is mob ID, x,y,z, current HP and mob type+maturity. Maybe also "spawn ID", for purposes like taxing. We know that loot is calculated at time of looting, and things like max HP/stamina and agility can be looked up in a "mob table" if you know mob type+maturity.
I guess you save some CPU by only updating the mobs in the "quadrants" where there are hunters. Current health could probably be updated by some sort of batchjob, but location would have to be updated individually - if you'd batchupdate the location all mobs would move at the same time which would make hunters seasick lol, also when changing the location of a mob you have to check for rocks and plants.
If you didn'e save mobs att all, it would mean it would be practically impossible to escape from a land area (for instance the merp land area near Silver Ridge TP, or the Falx LA around the "water plant") by moving mobs aside - as soon as you die and get to revival, the mobs on the way would respawn as they usually are. Also the server would have to spawn mobs around you when someone suddently arrives in an area, for instance by TP-chip.