Your question is good, but in responding to it, I want to replace references to the author of the poem (Poe) with references to the speaker in the poem. This replacement may seem to you to be a minor issue, but it's a huge one in literary studies. The poem stands alone and speaks for itself. (Without extensive biographical research on the poet, we can only say what the poem says, not what the poet thought or meant. To many literary critics, "authorial intent" is completely irrelevant.)

In rereading the poem before responding, it strikes me as worth mentioning that the speaker descirbes the raven as noble: it is "a stately raven" that does not hesitate or fear, "But, [as] with mien of lord or lady, perched above my chamber door - / Perched upon a bust of Pallas..." If it is indeed a messenger of Death, then it shows some of the Death's status in the poem, that is, Death is well above all common mortals.

A second item the strikes me is that the raven doesn't really communicate with the speaker. Its repeated one-word answers merely make the reader stumble to find meaning (e.g. ""This I sat engaged in guessing...") and, failing that, to despair.

The speaker may, in the final analysis, see death solely in terms of loss. Otherwise, the speaker seems to suggest, there's nothing to be learned from death: "Darkness there, and nothing more." Poe's poem might be showing us an existential crisis without any sort of resolution.

The enotes study guide to this poem (see the link below) has a section on the theme of "death" that you may find helpful.

In several of his dialogues, Socrates suggests the idea that knowledge is a matter of recollection, not of observation, learning, or study.  This philosophy parallels that of Poe's speaker in "The Raven."  For, as he has been studying, and he is fatigued and already in a melancholy state, his perceptions of the raven that appears over his door are purely subjective.  This perception reinforces Poe's comment that in his poem he explores as a Dark Romantic "that species of despair which delights in self-torture":

Then this ebony bird beguiling my sad fancy into smiling,

By the grave and stern decorum of the countenance it wore....

Then, methought, the air grew denser, perfumed from an unseen censer

Swung by seraphim whose footfalls tinkled on the tufted floor,

"Wretch," I cried, "thy God hath lent thee--by these angels he hath sent thee

Respite--respite and nepenthe from thy memories of Lenore....

And the Raven, never flitting,...still is sitting...

And his eyes have all the seeming of a demon's that is dreaming...

Clearly, the speaker looks "through a glass darkly" figuratively when he perceives the raven.  Perceived as a dark angel sent to presage death, Poe's speaker finds the most moribund of symbols in the raven whose deathly "Nevermore" resounds through the heart of the speaker, suggesting to him--not telling him about--the finality of the death of his beloved Lenore, resonating the "self-torture" of the despairing speaker.