I second that, some of these dramatic shots take tons of experimenting. They aren't easy to achieve. The shot I made took at least 20 tries and it didn't even turn out the way I wanted really.
I guess it's dependent on the skill level of the photographer. Experiment AND learn control of light. It will be much easier if you assign one job to a particular light when doing low key photography, and remember how certain configurations work in combination to give you a starting point.
And it's also not always about repositioning the light - you can also reposition yourself, the camera, or the model. There are many ways to go about adjusting for your lighting. If you know the characteristics of your light source well, it all gets much more simple.