I agree with almost everything you said, except for this:

> People who manage to struggle through it and create art are doing it despite their disease and not because of it.

While depression can hurt creativity––bi-polar disorder and schizophrenia can actually help it[1].

The discussion has mainly been around depression, but I think the "suffering artist" label can apply to a range of disorders.

[1] http://en.wikipedia.org/wiki/Creativity_and_mental_illness