you will have like 5 npcs in several good already existing spots that can be desirable. fire giants, red dragons, black demons, black dragons, kbd.. an argument can even be made for blue dragons, and some of the other npcs like otherworldly beings, chaos druid warriors, whatever

you should take a long look at the drop tables and balance them for what you want the eco to be BEFORE you release, rather than release and react. making a few of them op and ignoring others is bad and usually what we get from most servers, but giving them all some beneficial drops and reasonably comparable farm rates is the way you balance the game but also keep it fresh and keep the players looking around doing different things

dont make it easyscape but dont make most of them a waste of time either