The point of asking why she blocks bullets with her bracelets is about why she would need the bracelets. After all, when you shoot bullets at Superman they don't ricochet off him, so why would they ricochet off Diana? In fact, the bullets usually are shown to ricochet off the bracelets, which is the opposite of what you are describing.
And thank you for reminding me of the Holy Grail scene. I needed that laugh. But the better comparison is Metal Bat from One Punch Man.
Honestly, I understand why you enjoy the Eyes of the Gorgon moment you mentioned, it's a good and effective trope.
But I think this idea of neverending stamina makes Diana quite unique in pop culture and is quite thematic. What I think is so amazing about Diana is that there is something utterly resilient about her mentality. The idea that her friends and family can tremble and shake and she can be empathetic, while she herself never loses a step, makes for quite an energetic and vibrant character to me. There are very few characters with such an infectuous resilience.