Memorizing a few hundred lines of epic poetry probably is indeed unusual. But I bet most people have more than a few hundred lines of poetry in the form of song lyrics memorized (along with the tune of the song).

A lot of cultures that emphasize oral memorization will have things like this as memory aids

For example, Buddhist mantras have a specific way to pronounce, and if you alwaya do it this way memorizing becomes much easier

Or for a more Western thing, prayers also have a specific cadence that is learned alongside the text itself and that aid memorization