Seeing that cortana has lifespan of like 7 years, the arbiter is essentially victorious on Sangellios, chief still deserves a happy ending... The poor guy deserves a break....
-Master chief can save himself
-343i can't kill off Cortana (without bringing her back somehow) about as important a character as chief (so immediately protected)
Arbiter needs all the help he can get, he doesn't exactly have main character protection anymore.
[spoiler]Irrelevant to the arbiter we're discussing, but I loved [url=http://youtu.be/VkFj1JtZAyk]this[/url] scene from Halo wars. There need to be more combat scenes like this, hopefully with some elites fighting with Spartans this time.[/spoiler]