The Dungeon Alert idea is very interesting and, I think, very cool. It does, however, bring to mind thought...

...DA seems to be based around how "intelligent" creatures would react. Should DA events based on aggro from non-sentient creatures be different? For example, undead. Undead quests in general are built with the "here are 3 times as many beasties gather them up and kill them" mentality. And logically, non-sentient creatures shouldn't be able to mount the same level of coordinated response as sentient creatures. I would think that DA levels should never reach red when dealing with non-sentient creatures.

I know that may reduce the impact of the system toward its goal (reducing the number of "active" creatures in game) but it does make more logical sense and as such will meld better into the game.

In addition, DA in explorer areas... if you are going to implement it there, please, or please, add shrines in front of quests.