Compare her results with Linda Leaver's and Robin Wagner's. Despite having OGMs in Brian Boitano and Sarah Hughes, these ladies have not had a number of competitors make it to the senior level.
You do have to take into account, however, that Leaver more or less coached only Boitano from the time he was about 13 or 14 years old. From what I've read and heard, she was pretty much just starting out as a private coach (maybe had been at it for a couple of years already) when Boitano, at about age 8-9, showed up in a class. She continued with several students for 5-6 years, but as they dropped out, she didn't replace them with anyone else -- she concentrated on Boitano. She did coach Yvonne Gomez, too, who was competing for Spain and was a very good friend of Boitano's -- Yvonne has said Leaver took her on because Brian asked her to -- and Yvonne went to the 1988 Olympics. But Leaver wasn't teaching lots of students for the years that Carol Heiss Jenkins or the other coaches you've mentioned were. She was pretty much exclusively Boitano for about 10 years before his OGM, and then stayed with him as personal manager/coach after that.
That being said, I think CHJ is a fine coach, and she has as much chance as anyone of helping Miki. I think one of the most important things is to find a good coach-skater relationship. Each coach can "reach" different skaters in a different way. Most top coaches have a lot of the same skills and abilities -- maybe some are better at jumps, others at spins, others at choreography, etc., but I would guess most of them are overall pretty skillful. And yes, sometimes you need to go to someone who is particularly skillful in a particular area because you need that help. But finding the right "fit" with a coach is important, too.
I've always admired CHJ and hope she and Miki work well together and both have success. I think it's a good choice for her.
I always feel the need to change it every now and then and I realized that I haven't given Yuka a turn yet. Love her! 
