Phillip,
Of course the way to make mailing lists work with DMARC would be to
look at the headers and treat messages with mailing list headers
differently. Perhaps the issue isn't in DMARC but how the information
from DMARC is applied.
From my reading of sections 10.2, 5.2, and 15.4 of
draft-kucherawy-dmarc-base-04,
you can't do that and still claim receiver conformance with that draft
(although there's the question of whether one should claim conformance to
an informational draft in the first place).
Cheers,
Andy