Hrm....It's kindof like a -really really- dangerous hobby. You managed to do it a few times, you know your survival partly depends on your skills, but you -NEVER EVER- can be certain to survive the next encounter, or get out intact, not crippled for the end of your life.
As a player I'd not mind if highly mysterious, magical, and horror-overdose places/creature like Perfidus, Lich stuff would be removed or be accessible through DM quests only. Instead more higher level but mundane like enemies I would welcome, like lvl 18 bandits and highwaymen (outlanders!!!), falkovian raiders, invidian invaders (all higher levels), or sithicus with angry elves.
For me its never easy to face a stress-overdosing, super-duper magical maddening places like Perfiduse or Lich tower and get out sane, bragging about it.
They are pretty awesome for the thrill, but yeah inflates horror.
More mundane stuff all around makes encounter with an elite vamp more deadly. Actually I'd raise the difficulty of the terg ruins to lvl 17-20. And the wwolf lair also. To have werebeast and vampires the über-boss monsters in Barovia.
EDIT : Lol, but if it was up to me I'd max out magic classes on level 10 also
. So super-duper magic heroes dont overrun the domains. But yeah I am hardcore.