I agree with the importance of learning from good senseis and students. The students are sometimes even more important, since you don't practice waza or ukemi with the sensei most of the time. The best students at the dojo have definitely kept me on my toes, sometimes literally!
I'm beginning to wish there were instructional books about Yoseikan, though. Since I can't practice much by myself it would be nice to study the grabs and stances in illustrated form.