David Calabro (personal communication) wonders if the word shafts here (the reading in 𝓟 and all the printed editions) might be a mishearing for chaff (or, less likely, the plural form chaffs). Calabro notes that the following biblical imagery could be applicable in interpreting Helaman 5:12:
𝓞 is not extant for Helaman 5:12, but if such an error entered the text, it probably would have occurred as the scribe for 𝓞 (most likely Oliver Cowdery) took down Joseph Smith’s dictation here, although there is the possibility that chaff(s) could have been misread as shafts.
The problem with this proposal is that this Hosea passage does not really apply. In Helaman 5:12, Helaman is talking to his sons about the storm elements that Satan unleashes against mankind. Hosea 13:3, on the other hand, refers to how molten images will be scattered as chaff by the Lord. In Helaman 5:12, the shafts could figuratively refer to the spears, lances, and arrows that Satan throws at mankind (see definitions 1 and 2 under the noun shaft in the Oxford English Dictionary). A more likely possibility is that shafts refers to bolts of lightning that come with the whirlwind. The OED lists under definition 2g for the noun shaft the definition ‘a streak of lightning’, used poetically. Here in Helaman 5:12, “his shafts in the whirlwind” collocates with other specific storm elements that metaphorically come from Satan, namely, “his mighty winds” and “all his hail”. In fact, in a letter dated 27 November 1832 Joseph Smith used the word shaft with this meaning: “like as a tree that is smitten by the vivid shaft of lightning” (Doctrine and Covenants 85:8). Thus it seems very likely that shafts in Helaman 5:12 refers to lightning.
Interestingly, there is one Book of Mormon passage that actually uses the Hosea 13:3 vocabulary chaff and whirlwind:
In this case, the printer’s manuscript (the earliest extant source) reads chaff, not shaft(s). Once more, the context is different: in Mosiah 7:30, the text is referring to reaping the results of transgression. In Helaman 5:12, on the other hand, the reference is to the storm that the devil sends against us. Since the reading in Helaman 5:12 can be reasonably interpreted as referring to lightning, the critical text will maintain that reading (namely, “his shafts in the whirlwind”).
Summary: Retain the word shafts in Helaman 5:12 since the word here can be reasonably interpreted as referring to shafts of lightning in the storm.