I noticed this as well, after the mistlands update i played for a few days with a noticeable drop in fps and it was not too bad at first, I made a new character and started a new world, then when I got to the swamps suddenly everything got laggy and died a few times, then moving back to the meadows made no difference, everytime a boar or deer or greyling appeared the fps would drop to unplayable rates.

Then I tested it in older worlds with other characters and still the same thing. Im not sure what made the fps drop so suddenly when it seems okayish the first few days after the update. So i'm quitting for now until theres a fix or an explanation.

I'm not running any mods and i updated my nvidia drivers, and changed settings on my computer so most of the computer resources would be dedicated to running the game, but not a big improvement and I don't think it should be this way in the first place.