To me I’d rather there be an option that doesn’t require you to constantly create new games. As an option, it’s fine for people who want that, but other players prefer to play the same game for a while. How about this dynamic.
1: When you create a new game, the Terror Zone on creation is the one that is on the server for that hour.
2: You finish “clearing” the Terror Zone, and then a new random Terror Zone in that game becomes active.
At this point you have two options. You can leave the game and create a new game, that has the current server Terror Zone for that hour, or you can go clear the new Terror Zone.
3: After clearing the new Terror Zone, another new random Terror Zone triggers in that game (limited to a list of Terror Zones that have not yet triggered in that game). Basically, the Terror Zone in that game becomes disconnected from whatever the server is doing, so the Terror Zone only changes when the old Terror Zone is cleared.
This allows the Terror Zone feature to be used the way different players want to. The Type A farmers and grinders who want to just play the same Terrror Zone over and over will leave and create new games.
The Type B who likes to play an off meta build and thus takes longer to clear a Terror Zone doesn’t have to worry. If it takes him 80 minutes to clear a specific zone, that’s fine. The Terror Zone in his game is unaffected by what time it is on the server.
The Type C who likes the story/roleplay aspect and likes to play with a party gets to play end game acting like a rapid reaction force to wherever the hordes of Hell are invading this time. And sometimes the Terror Zone is one his character shines in, and other times the new Terror Zone is something a different character in the party can shine in.
It also gives a goal that people could try to attempt for bragging rights: Clear all the Terror Zones in a single game.
Of course, the question becomes how to measure “clearing” the Terror zone. It could be kill every monster inside, but I think maybe it should be killing Super Unique in that zone. I have a post with a more detailed list of all the Super Uniques in the zones, but every zone has one (except for Black Marsh, but you can just put Flamespike there). Maybe a few areas (like Tranvical) which has multiple super uniques you have to kill all of them.
If you buff the Super Unique in that area to “Terror” version of their basic self that would also give the Terror Zones a bit more challenge, and a bit more of the fantasy feel that Blizzard likes to have. And then it would make sense that when you kill the “boss” of the Terror Zone the terror zone moves somewhere else.