With the growing high level player base the demand for high level content rises exponentially. This being both for existing items/raids and for new content all around.
My suggestion is to make the Pandemonium zone instanced - like the model used in WoW for example. Let it be a 24-36 person zone (ie. 4-6 teams). This would kill the problems the playerbase is facing and would again require the players to put in some effort to reach their goals insetad of zerging.
The following could be an idea:
Since the initial portal mob Zodiac is already in place and the land between it and the actual first "island" of Pandemonium is seperated, then it should be possible to entirely remove the islands to an instanced area - ie. you enter Pandemonium like usual through the Ergo-portal from Inferno, the garden statues, and the land with Zodiac is still there, but behind Zodiac there is nothing.
Then when a raid force assembles in garden one person gets a mission from a quest mob. There are two missions - a mission for the Zodiacs/TNH and a mission for The Beast. This person updates all other people in the raid force with this mission by teaming them.
Now the raid force moves out, kills Zodiac and the portal spawns, but only members of a raid force can use the portal.
If there is one raid force only they all click the portal and end up in the same instanced Pandemonium Zone. The mission will ensure that no one unwelcome will use the portal and take a "spot" in the zone.
If two raid forces are present they will end up in each their instanced zone like two teams using the same door to enter their mission on RK.
Now they all move onto Beast or Zodiacs wether it's one raid force or ten, and everyones happy. A timer ensures that no person at any time can enter the instanced Pandemonium zone before 18 hours has passed for a Beast raid, or 6 hours for a Zodiacs raid.
I'm perfectly aware that this eliminates the possibility of killing two zodiacs and TNH otw to Beast, but I see that as a minor loss for the bigger and better picture.
Notice I have used elements that are all coded in the game somehow and working. All the land needed for the instanced zones exist already, and the coding for portals (or doors if you like to call them that) already exist.
/Av'
PS: Please feel free to come with suggestions and I'll try update the original post.