Is anyone else experiencing this problem?
Yes.
The Amigara horrors have the special attack [tt]fear_paralyze[/tt], which (if successful, high intelligence protects) takes 100 move points of the player character (usually a full turn). However that attack has a frequency of 0, which means the monster can do it every turn.
Now with several of those monsters, each does this attack every turn, which means the move point of the player character get never go above 0 and the monster have time to kill the character.
I suggest adding a timeout for that special attack. Other monsters have that attack too, but they appear as single monster and the attack is not always successful, so the player has a chance against those.