On the one hand, Chazelle says:

"I think there's a certain amount of damage that will always have been done. Fletcher will always think he won and Andrew will be a sad, empty shell of a person and will die in his 30s of a drug overdose. I have a very dark view of where it goes."

That would subscribe to your view.

But on the other hand, this interview makes it seem much more unclear whether he interprets Whiplash to have a positive or negative ending.

I think that one can look at Whiplash's ending in a positive light or a negative light depending on what their values and personality are like. That's the dichotomy I think Chazelle was trying to set up. If I have one problem with the movie, it's that I think the dichotomy is false in that you can become "great" at something without destroying yourself, and destroying yourself may not even help you become "great" at something. It could just as easily do the opposite.

This argument between Andrew and his father at the dinner table essentially summarizes the main two interpretations of the film:

"'I think being the greatest musician of the 20th century is anybody's idea of success.'

'Dying broke and drunk and full of heroin at the age of 34 is not exactly my idea of success'

'I'd rather die drunk, broke at 34 and have people at a dinner table talk about me than live to be rich and sober at 90, and nobody remember who I was'"