Does the division of the poem into stanzas, each with its final refrain, advance the theme and impact of the poem? Would some other design have been more effective? Why or why not?

The repetition of the refrain "Nevermore" is quite effective in emphasizing that the narrator will not get what he wants. The Raven is almost mythical, giving answers that cannot come from anywhere else. The stanzas have a lovely rhythm which can keep the narrative technique moving. Refrains always provide impact; the last word "nevermore" is indeed the last word for the narrator and for the reader.