Answering my own question on the wrong digital output being used on the CX20585 (hda/patch_conexant.c)...

Some of the the other HDA codec patches (patch_analog.c, patch_cirrus.c) use the first digital output node as the primary digital out, and set the additional digital outputs as slaves in codec->slave_dig_outs. Similar logic should probably be put in the patch_conexant.c as well, at least for the CX20585, to handle the multiple digital outputs.