From Dark and Darker Wiki
In my experience, you can crouch without jumping to dodge his Orb Attack if you are close enough - within maybe 1.5 to 2 halberd-lengths. But from further away, you will still get hit. My guess is that the orbs originate from a point slightly above players' head height, so the orbs naturally angle slightly downward. This would mean that walking towards the boss while crouching should improve your odds of dodging them. Jumping into a crouch should work at any range except maybe point-blank, provided you can time the jump correctly.
If you are close enough, you can also simply circle-strafe left to dodge the orbs - I don't remember for sure, but I think circle-strafe right doesn't do it.