It is a point of severe contention amongst psychologists, but Viking's right, in general, most reputable psychs wouldn't diagnose with DID, unless there really were no alternatives.
The triune god may or may not have dissociative identity disorder, but it goes without saying that he'd be diagnosed first as a dangerous sociopath, and would be locked in a mental ward, regardless.
Though, schizophrenia isn't exactly outside the realm of possibility, either...