Maybe I have a slightly different take on Dwight and Steve Earle. I really like them both, but you can tell that they came to the music from different directions.
Steve Earl is a writer and has managed to avoid the pitfalls that Nashville "stardom" offers. The need to produce product to feed the image invariably stifles a writer. You stop following your inspiration and begin to repeat yourself. Steve Earl continues to move in directions that the record labels can't handle (i.e., market). Substance use, I believe anyway, contributes to his career vicissitudes but doesn't (necessarily) dictate them. Whatever the cause, Steve Earl remains his own man and remains a vital creative force.
Dwight has always been about personality as much as music. He writes some, but has also developed his career using other people's songs. To stay fresh he has developed other creative outlets, such as acting, rather than exploring other styles of music.
Both of these guys have a pretty impresseive body of work out there. I'd be happy to be classed with either of them.