The Bronze Bow has some deeply defined characters so the concept of identifying them as heroes seems a little difficult. If we define "hero" as protagonist, the lead character Danie bar Jamin meets the description. We see the fact that he is driven by hatred beaten down until he is ready for something new. Because his character is so well-defined, we see elements that may seem anti-hero, but the more realistic the character development, the more this will always be true.
Joel bar Hezrin may similarly be called a hero; even though his mistakes are obvious, Joel grows and becomes increasingly caring. Leah, sister of Daniel, also emerges with heroic qualities. Thacia is a character who also falls short of all definitions of hero, but can be seen as a hero for women in this ultra-patriarchal society.
Samson is endlessly loyal to Daniel and seems to be unmotivated by anything but good. (Samson is the mute giant).
The real- life characters of Jesus of Nazareth and Simon the Zealot of course show virtuous and heroic qualities.