Actually, i think that there are 3 version of monks.
-The melee monk, big axe
-The ranged monk, throwing axes and they usually do die after throwing the axes
-The other ranged monk, throwing bombs.
The vamps i think have melee and ranged attacks, and they do transform into big vamps after being killed. Freezing them + Shotgun blast takes care of them;)
Your right Namur I may have been too hasty in my definatlys just watched a youtube clip of the second level and it appears they do actually die after throwing the axe. Its been a while sinse I played the game but I can't remember them doing that. Seems your game is fine Ossius just my memory being crap.