4.13 throws on my Gentoo install (since it wasn't available on Arch yet):

nouveau 0000:0a:00.0: DRM: DDC responded, but no EDID for DP-4

When this happens the console freezes unless I disable KMS via the command line
(SSH works fine).

My GPUs are 660ti in the second PCI slot connected to DP-1 and 1080ti in the
first PCI slot connected to DP-4.

Are you saying 4.12.11+ was supposed to resolve the random freezing?

On Gentoo I don't even have X install so I think it freezes when nouveau tries
to load the FB console.

Would it be worth building nouveau in instead of as a kernel module?