I've watched this clip a number of times and this is my opinion.
You can clearly see Lucic STOP skating at 0:05 because he see's miller is going to get the puck first. He is now gliding at this point. He continues to glide into Miller without any indication of avoiding him.
I honestly believe there was enough time to at least try and avoid Miller. Lucic does no such thing. His instincts kick in and it's just easier for him to run into someone as he is used to doing.
But, just because I feel there was enough time to avoid Miller, I think Lucic just reverted to his instincts and plowed Miller down sub-consciously.
I don't think Lucic is a dirty player. This was just a difficult circumstance. Besides, I think running into Miller is safer than trying to avoid Miller. ie. (knee to pad contact) could have blown out his knee if he tried avoiding Miller, etc.
Miller calls Lucic a POS