Priestly Backbiting in the Tanakh

[austendw]

This would suggest that the final version of the Numbers passage was written after this one. If we take the consensus dating of at least part of Deuteronomy to the reign of Josiah, this has to be an obvious problem with dating the final editing of Korah to the reign of Hezekiah.

Moreover, Deuteronomy 11:2-7 seems be to a later insertion.

Exactly so. That really does clinch the matter: Korah was not associated with Dathan & Abiram during the last years of the monarchy.