Re: The Validity of an Instructor
First, rank is supposed to be correlated with skill. That does not mean it is. Part of your decision-making process is balancing the learning model and access to talent and the practicality of commitment. Not students train to gain martial skill. There is an increasing number of practitioners whose goal is social community and physical outlet. While not negative, I would be critical of training under false expectations.
Second, most instruction will take on the flavor of the instructor, if not directly her personal influence. A zebra is not going to change her stripes. Watch or participate in 3 classes - if you aren't impressed, you're not gonna be impressed. The question then becomes, would you be satisfied with the training?
Third, a solid teaching model is going to clearly illustrate a path of education. There should be a "why" and "how" for what you do. Ikeda sensei is known for taking his movement, slowing it down and making it big to better illustrate what is going on. He also says that is what he is doing.
As a note of terminology for me, "brute" usual refers to the education of force. It would not be the term best describing aikido. To your point, the act of properly applying much of our waza should solicit discomfort.