Maybe, maybe not, only the Monster Manual can answer that.I wouldn't worry about it, it's a 20th level feature. I highly doubt that being very hard to kill with attacks will matter all that much then.
If you use just Player's Handbook as parameter then a Druid 20
will auto win against fighters, barbarians, rogues, monks and
probably rangers and paladins as well.
without spending any resource.
that's half of the classes in the book.
I doubt it will be any different with monsters.