> Armitage wisely avoids rhyme, unlike some recent versions – there is no evidence of rhyme in the original text
No rhyme in the original doesn't mean there should be no rhyme in the English. Akkadian and English are different languages. English verse rhymes.
> English verse rhymes
That is not universally true at all. For example, Milton's Paradise Lost, or much of Shakespeare. There are countless other examples of blank verse in English.
A significant portion of the English canon of verse doesn't rhyme, from most of Shakespeare to Milton (the latter who called rhyme "the invention of a barbarous age"), from the Anglo-Saxon era all the way to the twentieth century.