I know this thread is old now, but I couldn't help but think about the Circle of Eight as we near the eventual release of chapter 2.2.
After reviewing the info that we have, Circle of Eight , here is my theory on the circle of eight.
There are lots of references in libraries and archives which suggests that the Circle of Eight was an old cult. There is belief that the Circle of Eight has something to do with the pulse. I think that Iso-8 is a result of the pulse which someone created using information that they gathered from the Circle of Eight or someone reforming the Circle of Eight itself. The Circle of Eight is dedicated to creating and using Iso-8 for promoting chaos.
Now I think, what is currently happening is that there are lots of organizations running around trying to get information from the Circle of Eight so that they can use iso-8 for their own personal goals. These organizations are the Hellfire Club, the Hand, Hydra, and others. This will allow for introduction of people such as Shaw, the Mandarin, and the Kingpin as they start acquiring more powerful goons from what they are learning from the Circle.
I think we'll end up with a lot of people using the Cricle for their own gains through alliances but not actually becoming cultists themselves. Those who will actually be part of the cult will be people more dedicated to chaos and probably followers of Blackheart.