Though the visible content of life's struggles is widely variable, the core themes in people are identical. Observations and descriptions of individual differences are, of course, extremely valuable in making counselors mature and case-wise. But we should be agnostic about personality theories. On the surface such theories are speculative, prone to intellectual fashion, and prejudiced by their hostility to what is true and significant about people. Even more important, personality theory turns out to be absolutely unnecessary for effective counseling.
Personality theory is even a distraction because it directs attention to the wrong questions.
It mistakes the fascinating but superficial for the significant. It buries significant clarities that the Bible provides beneath superficial ambiguities that psychology attempts to explain. The questions that personality theory tackles are interesting subjects for general scholarship. They are perennially vexed because they are inherently ambiguous. But the Bible addresses in practical detail the significant things good counseling must address.