You should be able to take him out with a single headshot, not sure what's up with that. But I did mess up the collisions slightly so the arrow sometimes gets deflected by the character's overall capsule collider. The AI also did need a bit of work to allow them to step up and down large platforms. I did fix most of these cases after the jam, but I didn't feel right about updating my game after the submission period.
BTW thank you so much for playing! I really loved your game!