In my experience, no character is or should be completely without flaws, issues, or fault. The characters we create emulate the people in our lives, and since those people are imperfect, so to should our characters be. The more flawed or abnormal the character, the more compelling the story, right? Well… sort of. Within limits.
Your characters should be more than the sum of their parts. Incidental side characters may be an amusing bundle of neuroses, tics, and habits, but you can’t build an entire narrative around someone like that. There needs to be more there than a list of long condition names from the DSM IV. If a character does operate with or suffer from a mental disorder of some kind, and it’s simply a part of the character rather than their entire being, you need to consider how that disorder is portrayed.
Take Sherlock Holmes, for example. From the beginning, Sir Arthur Conan Doyle’s consulting detective has been single-minded, selfish, insufferably arrogant, difficult to work with, and at times nearly impossible to access on an emotional level. His modern BBC incarnation self-identifies as “a high-functioning sociopath.” Yet this is not the only aspect of his character. There are people he cares about and will go to great lengths to protect, and as intolerable as his behavior can be, he really does believe he is helping people more often than not. His disorder is not portrayed with the sole purpose of being laughed at, nor is he held up as anything towards which we should aspire.
John Green often challenges us to “imagine the other complexly.” We need to see beyond what could be considered stereotypical behavior and bring across the hidden depths of a character. Sherlock Holmes or Sheldon from The Big Bang Theory or Miriam Black would be what doctors would consider ‘special cases’, people so wrapped up in their complex issues that it can be hard to get to the person that lays underneath. And there is a person in there, beyond all of the neuroses; and like all people, they have feelings, aspirations, doubts, and vulnerabilities. Part of the reason I have trouble enjoying Big Bang is that I often feel that Sheldon is not being complexly imagined; rather I feel that his neuroses are simply being played for laughs, and that we are encouraged to laugh at him, rather than with him. There should be more to him than a haughty superiority complex and a bundle of nerd culture references, and things beyond those facets seem difficult to find. But, that’s just me.
What I’m driving at is this: imagine your characters complexly. No matter how special their case may be, they have wants and needs to which readers should be able to relate. The deeper your characters, the more they will enhance your narrative, and the better your story will be.