The PHB2 Errata doesn't mention anything about 0-level spells, either.
As for the Tanarruk Demonsword, it would actually make a bit more sense for them to be Hobgoblins, who have an established Duskblade tradition (at least according to MM IV or V, anyways, where statted Hobgoblin Duskblades appear). Or I suppose that the Tanarruks could have learned from the Hobgoblins, which makes some sense as well.