2c-b is off-the-list because from what I've heard they are psychedelic, but not as mind-expanding as LSD, according to Erowid and many of the experience reports I've read, so I'm guessing it doesn't have psychotherapeutic potential.
Although I agree with your assessment of 2C-B as less mind-expanding, I don't think that that means that it doesn't have therapeutic potential compared to something like DMT. In fact, I believe the opposite is true.
With something like DMT, the experience is so fast, so intense, and so otherworldly that, although you may "learn" something from it, what you learn is not going to applicable to the real world. In the smoked form, at least, I don't think DMT has any therapeutic potential. It's interesting that a drug like DMT
exists at all, but as for what it's
good for, I'm not exactly sure. Probably not therapy or personal growth
2C-B, on the other hand, induces a milder altered state, but that doesn't mean it's less useful. In fact, the things that you may observe about yourself from the perspective of the 2C-B altered state will probably have far more relevance to your everyday life than something you might learn on DMT. For example, on 2C-E, I was drawn into a memory of my father attempting to spank me with a belt in the manner of his father, to discipline me for something I had done wrong. Instead, he broke down crying, and hugged me. I realized then that my father had made a conscious decision to raise me with love, rather than the disciplinary upbringing that he had experienced. This is not something that I could have realized on DMT, since the concepts of "I" and "father" and "love" are completely and totally obliterated.
In summary, I would encourage you to avoid writing off 2C-B, or at least to avoid writing off the 2C series as a whole. You should certainly try DMT if it's something that interests you, but I've found that I generally learn more from, and get more out of, low-dose, thoughtful trips based somewhat in reality, rather than ego-crushing 35mg psilacetin mind-voyages, for example.
For reference, here are my 2C-B and DMT trip reports:
http://www.erowid.org/experiences/exp.php?ID=75201
http://www.erowid.org/experiences/exp.php?ID=71099