Regarding the bolter thing, presumably the bolter rounds that tore away his vox and clipped his shoulder didn't detonate on impact? Bolters in the fluff are far more lethal than they would appear in the game, there's no way a human getting hit anywhere near the face would survive it- their head and most of their torso would be obliterated. Even a round clipping a shoulder guard would tear away the shoulder guard or throw the arbite backwards a few metres.
I think it was just for dramatic effect! Maybe, if the story was allowed to run, I could have shown my Arbite as being seriously injured as well!
Never got the chance unfortunately.
You might be right about Alpha's. I suppose I could have used another bad guy!!