I looked at all your drawings. I think they're really good, but there's several really important shots that you missed that are critical for setting the mood for scenes you drew in comic book form.
On your Halo 3 Practice page 4, there's a shot where Sgt. Johnson lets out a sigh of smoke. This is important because it adds a feeling that this is a depressing scene, but all Johnson is allowing himself to show is this sigh. He is only allowed to give this sigh because he is a soldier.
On Halo Practice Page 5, there should have been a whole body shot of Johnson holding Cortana's chip instead of Chief standing. This way you can make Chief's hand more surprising. The next page can be only chief standing, making it WAY more epic.