There are many ways to skin a cat and for such an interesting subject you can introduce many taxonomies. First I would point that regardless of the categories, most likely they represent a snapshot in a life of a mistress. Today's dungeon mistress can and many times will be tomorrow's indie, and what a mistress does or does not do will change in time.

One interesting (to me) classification is reactive versus proactive. By the nature of the job a mistress tends to become reactive because she has to respond to the first move made by the partner. There are though a minority, like those running the forums, creating studios or other related businesses who are proactive.