The huge knight (the fiend) is not pushed away when I activate my shield. This caused me to get stuck, as it just kept attacking me while I was trapped behind it (doesn't seem balanced), and because it is only invulnerable from behind, I was unable to do anything.
Those enemies are called Trojans and you're talking about "Corner locking" this is normal for Trojans to do if you don't know how to properly fight them, it's not really unbalanced as long as you know how to move around them.