Hei lovely people,
Finally can manage myself to have an account in here.
So, Headstrong. In my personal experience. She is really good. Not great but very good as a Bronze who I think worth to be Gold. She helps me A LOT during my early level.
She is able to get the jobs done. Due her ATK and Armor Break stats a bit far from Understudy, she can finish your enemy quick and clean!
The only complain about her. HP and Defense. A bit lower than Understudy. But that's about it.
Lemme give you perspective from a player. When you fight an AI. I feel like Understudy is better than Headstrong (because she is defense oriented). That's it. But as a player, Headstrong far more rewarding..