πὰρ δ’ ἑτάρους δυοκαίδεκα πάντας ἀρίστους
We have seen in several places that, in the theme of ambush, it is the best, the aristoi, who are chosen for such missions. The thematic association of the best seems to be so strong that it applies to the victims of the ambush here as well. It would seem to apply to Rhesos in particular on the deeper mythic level, in which Rhesos is a grave threat to the Achaeans.