Bauckham has done good work in this essay comparing the misfortunes of Tobit and Sarah to those of northern Israel, so that the Book of Tobit is in some sense a "parable" of Israel. He also is able to establish the book's strong anticipation of the return from exile of the northern tribes. This is all in the first half of the essay (pp. 140-54).
However, Bauckham then shifts his focus to the intended audience of the the book, and argues at length that the audience is these exiled northern tribes. Actually, the problem I see is that he does not argue this precisely, he merely assumes it, but rather he argues for the existence of the northern tribes as a distinct people in exile so that they can then serve as the audience for Tobit.
I suppose he has done an adequate job at the task he set for himself. Whereas almost all scholars assume that the ten northern tribes, not long after their exile by the Assyrians, assimilated into the cultures of those among whom they now lived, thus ceasing to be a distinct people, Bauckham argues that this was not necessarily the case. He can cite some evidence:
- The Israelite exile involved numbers of exiles large enough to maintain distinctiveness in a foreign culture.
- A hope for returned Israel is expressed in some of the biblical prophets (Jeremiah, Ezekiel, later parts of Isaiah, Zechariah, deutero-Zechariah).
- There are some theophoric names referring to YHWH in Assyrian texts continuing until around 600 BCE.
- Josephus and others locate the northern Israelites still in Media and thereabouts (Ant. 11.131-33).
- In Rabbinic times there were still Jews in this area, and they were probably actually descendants of the northern tribes.
The only texts that Bauckham is able to cite that do express hope for the return of the northern tribes are Judean texts (the aforementioned prophets), as Bauckham recognizes (pp. 156-57). Doesn't this prove that (some) Judeans harbored the hope for the return of those northern tribes as fellow-worshipers once again of their shared God in a shared Temple in Jerusalem? After all, the Judean prophets predicted precisely this, and the disappearance or, at least, non-return of the northern tribes would surely have presented to the Second Temple Jews--who had experienced their own exile and return--a grave theological problem regarding the justice and faithfulness of their God.
It seems to me that Tobit would work well as a text composed for Second Temple Jews in Judah who wondered about the faithfulness of their God because their own return from exile had not been nearly so glorious as the prophets had advertised, partially because the northern tribes had not returned at all. In this perspective, Tobit would have been written to assure Judeans (not exiled northern Israelites) that God would be faithful to his promises to restore the Israelite exiles and thus re-unite all the tribes, presumably under one leader and in one kingdom.