There's a simplicity and directness to your poem that, while I can't imagine Hermione writing it, I can imagine a younger Hogwarts student penning the lines with the earnestness and solemnity of a bedtime prayer, saying "We must remember the dead every night before bed.

The lines "All creatures have done their parts, though many have broken hearts" was touching and evoked the sacrifices made throughout the books.  I agree Voldemort won't be missed, and if you edit the last word, you'll have "hiss" instead of "his." :)