I confirm that it's The Vault 4.0 which introduces that encounter. Once you manage to defeat the Greater Werewolf, you will see, looting his corpse, why it was such a hard fight. I suggest you to go back when your experience level is high enough...
Only Fields of the Dead and Vault 4.0 the greater werewolf is in the last room, the room of the treasure. In the original game there was only a vampiric wolf. Now the dungeon is full of vampiric wolves and death dogs. Excuse my english ok? I am from Spain