Just like in the Worldstone Keep, if guest monsters were to appear in TZs, it could improve monster density and even make less popular TZs a bit more appealing.
Alternatively, I think it wouldn’t be a bad idea to have monsters periodically spawn around the player, similar to the Pandemonium event.
One more idea to add: I personally think it could be interesting if a boss monster had a low chance to spawn when defeating monsters in TZs.
terror zones could have been made so much more fun and challenging! Can you imagine the new uber bosses that can appear in them? or even ester eggs like 2 Uber bosses in the same zone? It’s obvious that it’s not "Blizzard North / blizzard anymore as the developer of the original! It’s Microsoft developers who never played the original! That’s why a lot of strange design things are added “Sunder charms”? ruining the whole core game! Or runewords that adding nothing just Choas - Like Mosaic ? its a joke! to be honest!
Yes they basically created the structure for Terror Zones but didn’t spend time detailing it, which is insane.
Terror Zones should have lived up to its name. Any zone such as Cold Plains should be Terrifying to enter when corrupted by TZ.