As I have said many times before this scenario more than any other scales in difficulty with the system mastery of the GM that runs it.
No group who plays this event should expect to survive.
It is highly possible that the entire party would die in the first encounter (especially if they failed to win initiative).
Giving a GM highly intelligent opponents, who have been around for a very long time, with access to a very flexible spell selection (wish I am looking at you) means that the more the GM knows about what can be done the more options they have to respond to a party.
This is why I will never play this scenario. The only way I think that I should be allowed to 'win' is if the GM softballs or does not have sufficient system mastery. (my opinion, your mileage may vary)
