Here in the printer’s manuscript, Oliver Cowdery initially omitted ye are. He later supplied the two words, perhaps when he proofed 𝓟 against 𝓞 (the supralinear ye are was written with slightly heavier ink flow). In any event, the sentence here definitely needs a subject and finite verb. Although 𝓞 is not extant, it probably read “ye are heaping up for yourselves wrath”.
Summary: Maintain the corrected reading in 𝓟 for Helaman 8:25: “ye are heaping up for yourselves wrath against the day of judgment”; the initial text in 𝓟 without ye are seems to be the result of a simple scribal error.