Thanks for the much needed feedback! The monster behavior is something I definitely want to improve. Now that I have the main level greyboxed and there's enough space I'm thinking of giving her chase and patrolling modes. Maybe the chase triggers after she sees you and then instead of a movement every two notes she randomly switches between moving on every note and every two notes. That along with some penalty for missing a note might make for some tense situations.
And I'm not sure if I'll have time to work on varied beat patterns but I agree that it would make things more interesting T_T