I'm reading 'Residence on Earth' by Pablo Neruda. He's a South American poet who spent five years in the far east as a consul, and he wrote this during that period.
They speak essentially of his spiritual isolation and alienation. His poetry I imagine was a response to this suffering.
His famous youthful song was called 'twenty love poems and a song of despair'. Despair for him then was a minor note, in 'residence' it becomes a kind of existential crisis. Later, he repudiated the work as it for him was a song of death. He'd moved beyond that singular point (so in a sense that point was not singular).
Rilke often spoke as silence and aloneness as a condition for his poetry. Whereas for Neruda it was put upon him. It's not enough of course to have these feelings in a deep way, plenty of people have them without becoming artists, one must also have the talent and opportunity to learn to express it.
If art is the response to suffering, then it is not surprising that madness, and so called schizophrenia is associated with it. They're the outward form in the personality of an inward singularity.
Having said this, Susan Sontag (literary critic) said that there is a certain fetishisation in european culture that asks its artists to suffer as a sign of authenticity. Could this be connected to the suffering christ? Just because europe has desacrilised over the last century or so, does not mean that the inner form of its spirit is dead. John Gray (philosopher) wrote of both communism & capitalism as being forms of christianity on the level of ideology. What is true on a political level could also be true on an inward level.
Tagore, an Indian poet, rebuked his fellow poets for embracing European modernity, as a contracting movement rather than an expanding one. One should note that modernity was born after European-wide civil warfare. One could suppose that modernity was a reaction to this, certainly Dada, Surrealism and Primitivism was. Although there are notes of melancholy, there are moments of transcendence, joy, hope and enjoyment of sensuality in Tagores poems.
There is also a romantic ideology which elevated sensibility against an increasingly materialistic & industrialised European society.
I'm not sure one could characterise Rilke as being incredibly productive, he wrote little and slowly (the duino elegies took ten years), but what he wrote was of lasting significance and read still today. He is essentially a religous poet, a poet of the sacred.