The 1874 RLDS edition added the definite article the here before saints. This reading has been kept in the subsequent RLDS text. Most probably the original manuscript did not have the the here (since both 𝓟 and the 1830 edition lack it). Elsewhere in the text, there are nine references to “the blood of the saints” and one to “the blood of his saints”:
Moreover, the phraseology in Mormon 8:27 is similar for most of these other examples: five cases refer to the cries of the saints or of their blood, and seven state that the petitions of the saints are directed to the Lord (“to God”, “unto me”, and “unto him”). These similarities argue that “the saints” is expected in Mormon 8:27; Oliver Cowdery, the presumed scribe here in 𝓞, could have accidentally dropped the definite article when he took down Joseph Smith’s dictation. Oliver’s occasional loss of the definite article, if only momentary, is fairly common in the transmission of the text (see the examples listed under Alma 14:5).
Note, however, that for Mormon 8:27 the definite article the is conspicuously lacking in the larger passage when referring to various groups of people, all in opposition to the saints:
The text does not read “the secret combinations”, “the churches”, “the leaders”, or “the teachers”. The use of saints without the earlier in verse 27 is consistent with this usage and may therefore be intentional. The critical text will therefore follow the earliest reading in verse 27, without the definite article before saints.
Summary: Maintain in Mormon 8:27 the earliest reading without the before saints; the larger passage avoids the definite article for other nouns referring to groups of people that oppose the saints.