Sean, Sean Tully can shed some more light on this, but as far as I know, Hunter worked with MacK on most of his California courses, including Meadow Club, CPC, Valley Club and Sharp Park. Valley Club is where I think Hunter had his biggest role, and also in a sense ended their run together. Hunter sort of "came out of retirement" to help out with the Sharp Park project from what I've read.
I think Russell does get credit, at least here. I know those in the know in Australia certainly give Russell credit for his efforts. As far as an official, formal partnership, if there was one, I don't recall.
I'm not sure the realtionship with Jones can be called a partnership since they did all of one course together and Jones had never built a course himself before. I think Jones gets equal billing for the obvious reasons, he was Jones, he was part of the consortium and it was his dream. I think he gave generalities of what he wanted, but MacK was the architect. Afterall, why else would Jones be looking for an architect in the first place to build his "homage to St Andrews"?
As Tom D has stated before many times, there is a common thread throughout all these realtionships, and that is MacKenzie. Is it mere coincidence that these people came along with special talents needed for the job and MacK was able to just walk away and a world class born sprang out of the ground? Anything's possible, but highly unlikely. MacK's ability to quickly find the person who could carry out the task at hand is a talent in of itself. How may Ross courses, for example, where they have been labeled as "mailing it in" and having never visiting the site turned out mediocre because Ross had no idea who it was that was implementing his design? Quite a few, from what I understand.
Perhaps all the top quality guys that you mention became such because of the working relationship that they enjoyed with MacK. In other words, he taugtht them a thing or two. In addition, I think MacKenzie was very charismatic and knew how to take control of a situation. People for the most part seemed to be drawn to him. And he was very experienced by this time after leaving the UK, an experience I'm pretty sure that Maxwell and Hunter did not quite have yet when meeting him.