Here we probably have one more case of scribe 2 of 𝓞 leaving off a plural s (see the list under 1 Nephi 13:23). This conclusion is supported by the use of the plural verb were. This use of were shows that there was no proximity effect from the preceding singular nouns face and earth that could have led to was rather than were.
The 1830 typesetter reconciled the subject-verb disagreement by changing the verb were to was. Joseph Smith, in his editing for the 1837 edition, correctly restored the plural dominions and reintroduced the original plural verb form were.
Summary: Maintain Joseph Smith’s restoration of the probable original reading in 1 Nephi 14:12 (“their dominions ... were”).