I really wonder how much design influence JN has on his courses? He is responible for dozens of courses and I would bet he has trouble remembering the course names/developer's name/city/state/and who on his staff is the lead architect.

My best guess is that other than when he visits each course in person, he has very little to do with its design, he goes out, makes comments and changes and after he leaves, a portion of those changes are actually done.

Michael:

Once in a blue moon, it's me.  

From what I've seen and heard, Nicklaus and Fazio are pretty different in terms of how they put time into their projects.

Jack is contractually obligated to spend less time on his overseas projects, but for all the "signature" designs in the USA, I think he tries to spend approximately equal time on all of them -- partly because some contracts specify a certain number of days, but partly because he is very intent on the client getting what they pay for in terms of his personal time.

Fazio seems to understand that certain clients don't care so much about how much time he spends personally on their site, and others want him more involved, and seems to feel more free to divide his time accordingly.

As to who really does the work, both of them have deep organizations with a lot of talent, and that makes it hard to divide up the responsibility for their success.  Plus, there are generally as many versions of "who did what" as there are people on a job.