Holmes is an INTP. However he is also a cokehead and the cocaine messes with the outward perception of his persona. For example his ability to be a super sensor is contrary to most INTPs who are mostly oblivious to much of their environment but the stimulants turn this around. The Ti/Ne suddenly takes in massive doses of sensory information acutely, like a fresh vein, and processes it to the point of appearing godlike in his observation ability. Prolly prefers his violin playing coked out better too.
Naturally the negative effects of the coke although not emphasizes as much in the stories also distort his personality.