Pandoc processes a wide variety of inputs, including DocBook.  I use
this to process both DocBook 5 and AsciiDoc, the latter via Asciidoctor
since it's not supported natively.

Attached is a DocBook 5 file which contains two portions of verse.  The
first is in an epigraph, while the second is the main content of the
article.  Both contain a literallayout with the class "normal".
"normal", as opposed to "monospace", indicates that the text is printed
in a normal (usually proportionally spaced) font, and is the ideal
choice for verse.  DocBook 5.2: The Definitive Guide[0] specifically
states that the default presentation is "normal" and that literallayout
does not intrinsically imply a font change.

However, pandoc doesn't honour this correctly.  For instance, when
generating output for troff -ms (which is great for rendering in the
terminal), pandoc puts it in a constant-width font, which is not an
appropriate presentation.  (It also mismatches beginning and ending
directives.)  I've included an example of this as an attachment.

Similarly, when outputting for AsciiDoc (which I know has a verse block
specifically for this purpose), pandoc also produces output which
renders in monospace.  I've attached this as well.

I have not tested every output format, but I expect they'll all function
the same way.  I realize that some output formats are insufficiently
rich to deal with this case, which I'm obviously not expecting to be
fixed, but it would be nice to be able to properly process files
containing verse or other non-monospace whitespace-sensitive blocks.

Commands used:

    pandoc -f docbook -t ms -o dark.ms dark.dbx
    pandoc -f docbook -t asciidoc -o dark.adoc dark.dbx

groff output:

    % groff -ms -Tutf8 dark.ms >/dev/null
    troff:dark.ms:4: warning: cannot select font 'C'
    s.tmac:dark.ms:12: error: unbalanced .QE
    troff:dark.ms:15: warning: cannot select font 'C'

Please let me know if I can provide more information or examples to make
reproduction easier, or if you have questions about usecases.

[0] https://tdg.docbook.org/tdg/5.2/literallayout