It is quite obvious that the verb were was accidentally dropped here when copying from the original manuscript to the printer’s manuscript. The 1830 edition, copied here from 𝓞, has the were. Clearly, the clause would not make sense without the verb. It is true that in certain cases the linking be-verb is missing in the original text of the Book of Mormon, but all these examples seem to be restricted to quotations from Isaiah (see the discussion under 2 Nephi 13:14).
One theoretical possibility here is that the original text (or 𝓞 itself ) read was rather than were. Even so, the subjunctive “save it were” is considerably more frequent in the earliest text than the indicative “save it was” (for some statistics, see under 1 Nephi 17:31 as well as in the addendum for that passage at the end of this part of volume 4). Also note here in Mormon 6 another example of this phraseology:
Thus the odds are quite high that the original text read were in Mormon 6:11, in agreement with the 1830 reading there.
One other possibility, but quite implausible, is that the original text here read “save twenty and four of us”—that is, it lacked both the it and a verb. Usually the function word save is followed by a clause, but there are some examples of save followed by a noun phrase in the Book of Mormon text. Compare, for instance, the contrastive usage in the following passage where both the noun phrase and clausal types occur:
But here in Mormon 6:11 both 𝓟 and the 1830 edition have the it, which argues that it was in 𝓞 as well. The original text undoubtedly read “save it were twenty and four of us” in Mormon 6:11.
Summary: Maintain in Mormon 6:11 the subjunctive were in the phrase “save it were twenty and four of us”, the 1830 reading.