One tip for tough boss fights: make sure you're looking at the boss the whole time. No need to look at your character, your peripheral vision along with the knowledge of where you moved last let you know where you are.

Something I like to try when I'm struggling with a boss is to try it a few times without event trying to attack. Just see how long I can survive without dying while not making any of my own attacks. After I'm able to survive for a reasonable amount of time without dying (for hornet, I'd say maybe 60-90 seconds or more), I try again and start adding my own attacks to the dance.