That is precisely why I pay extra to have White Rose portray Dr. Squalus and relegated Alex (Bald) to Evil Assistant! I could cut my costs in half if I let him play the doctor, but his default is a goofy goon character. Maybe it's the influence of "Ilsa: She-Wolf of the SS" and the Italian knock-offs that followed, but I find an evil woman torturing a poor girl to be much better than a heavy-handed man dominating a submissive prisoner. I paid extra to have Rose be the torturer in my "Preparing for Surgery" series, because I prefer "a woman's touch" of evil. I also selected her because I like the contrast of the blonde dom working over a brunette sub. Maybe it goes back to the whole Master Race imagery of the "Ilsa" movies, but so far it's worked out precisely how I expected. At least for me. My second choice for a Dr. Squalus would be a redhead. Again, for the contrast.
The one exception to a blonde dom was the initial treatment for the PfS script, which was "A Strange Dream" with Anna and Alina. Alina was a dark-haired evil doctor and Anna was blonde, so it was a good contrast. Alina had a stronger build than Anna, so it was natural that she would be in the dominate role. It also helped that Alina was more experienced in Cruel World films as a victim, so playing a dom was a new angle for her, and Anna was a natural submissive. They were also friends in real life, so there was a good repertoire between them. As an aside, the "between takes" video I received was hilarious! Anna struggled to keep a straight face as Alina tried to act evil.