You have to make a wee distinction IMO, between "experiencing, and having experienced, extreme states of pain/depression/turmoil...etc."-
which is linked with heightened sensibility/perception, or results in traces of it, and the act of creating [which integrates these visions arising from the heightened awareness] in itself, which often cannot be acted out if the state of chaos/depression/pain is severe and serious enough...
Sometimes you have to regain partial balance before any sort of creative work is possible- Compare it to a heroinist, he can't do any creative work on junk whatsoever, because the extreme state of numbness narrows not only his mind, but also his body... (completely random example, not a personal one BTW)
From my own experience with depression/anxiety/complete suicidal mindfuck chaos, I had periods SO dark and down I wasn't able to talk, eat, move or get out of bed at all, do anything at all... Creative work was impossible, I had to get some sort of basic, cognitive functions to return before being able to distill my experiences and moods into art in ANY form...
So, to sum it up, yes having that DARKNESS EXPERIENCE make you create brilliant art [sometimes], and it make you feel stronger and deeper, see further and more intensely than anything experienced in a "normal" state of mind-
But in my opinion, if the feelings are too overwhelming and serious, it will stifle you and make work difficult, you need to have some kind of autopilot ability (and in total depression, you lose that, 'cause you have no will left to do anything) to be able to merge art with experience...