Forgotten Tower? That is its own Terror Zone.
Depends on The Terror Zones. Blood Moor and Den are specified as part of the same Terror Zone. Maggot Lair is not part of the Far Oasis Terror Zone though.
Currently you can either go somewhere else in the same game (not a Terror Zone) or create a new game to run the same Terror Zone again. I too agree that it would be more fun if a new Terror Zone spawned.
I have a thread where I list suggested improvements, and that is number 5 on my list.
If you think that is a good idea, please comment in my thread so that teh Devs might pay attention to it.