Some thoughts of mine about the subject.
I think the system has several layers, that must be combined.
When we get the perfect combination, we also get a payout that is maxed.
One layer is personal, based on avatars stats (including equipment used),
another is region based, next is mob based, and so on.
Too complex? Nope.
Every spawn is a "spawncluster", meaning every mob isn't on a individual
spawn point, it's controlled of a larger "spawncluster".
There can be several "spawnclusters" in same area. Look at Boorum spawn,
there are (at least were) three "spawncluster".
The boostsystem (globals) are moved in a scheme and activate
these "spawnclusters" due to certain conditions (time, max amount of
boosted loots, and whatever rule that fits the system) making them open
for players to grab. There are absolutly no garantuee to get a global
while these "spawnclusters" are active. The personal layer must also be
active for boosted payout.
Now, remember that a lot of calculations can be reduced by using dynamic
code.
So what might look complex, due to a lot of things has to be combined,
might actually be quite simple in the end.
This is just a small part of the whole system, so don't see these ideas as
the only thing that controll the loot. There are way more parts involved
imo...