Read this one probably pre-1996. Set far in the future. There is a high-tech society living in a dome/force field type city, eating pills and very intellectual, not much social interaction. The rest of humanity is primitive - bow and arrow hunter society - and unaware of the high-techs. Lots of loners, with small bands of outlaws to avoid. Some creature is killing people in the primitive society but it turns out the creature is actually one of the people, who is kind of possessed or something. One of the hunters ends up finding the city in the end.

I know, not a lot to go off but it's been a long time. If someone can successfully ID it for me I'll shoot you a book credit. Thanks in advance for any help!

 A lot of the elements you list make me think the book you are seeking is "Wintermind" by Parke Goodwin and Marvin  Kaye.  It is the seond novel in the "Masters of Solitude" set.