I can say I've had enough night creatures for a lifetime, or at least for a few forts.
My last fort was lost to a tantrum spiral caused by two werebeasts in quick succession, both of which managed to infect someone in the military (a wereotter and a werecoyote), while I was already dealing with finding the vampire that was somewhere roaming my fort.
Ironically, the vampire was instrumental in the slaying of both werebeasts... I should have noticed something strange about a Master Speardwarf, Dodger and Shield User (and Liar) in a fortress with barely any military training.
And the fort just before that had a vampire too.
How long are you letting the history gen run? I usually stop it at 120 years, or less, since on this crappy pc it takes 30-40 seconds to process from year 100 to year 101, and the few times I've let it run unattended up to 250, it crashed mid-way.
Young worlds might have more night creatures if they're slain by heroes during history.
Try also increasing the number of beasts in the worldgen parameters, I always gen worlds on "high" or more.