Its not Dark Souls level. But most of these bosses will take a few tries. Timing your dodge is key. Jumping before aiming your bow is huge, the slowmo makes it not only easier to aim but gives you time to breath for a sec, watch a boss winding up and better learn its attack - all bosses in this game have obvious telegraphs for their attacks if you slow down and pay attention, and the dodge window is generous. While I found a couple bosses surpisingly easy, most you can expect to die to 3-4 times at least as you learn the battle. Kena has a tight, focused combat kit, you are not expected to learn a ton of weird combos or abilities, but master what she can do.
I love love love this game. It prunes away so much modern game bloat, no xp, no gear grind, huge skill trees, endless cutscenes and character chatter, no massive open world to traverse because this game just doesnt need one, its not interested in wasting your time. GOTY for me no joke.