These are some of the mistakes I was referring to earlier. In college, Miller's ability to break up plays around his own blue line was one of his biggest strengths. At the NHL level, he's learning when that is going to work and when it is not. That's going to have to come with experience. He's still breaking up these types of plays on a regular basis, but when he gets burned, he really gets burned.
EDIT: To add to this thought, I don't mind seeing these types of mistakes from young players so long as they are learning from them. These types of plays are the difference between a player trying to make an impact and a player just trying not to make mistakes. I want Miller to keep trying to step up here but pick his spots better. If he were to abandon it, then he may be on the path to "solid but unspectacular".