As far Chief's face... so what? We already knew he's a middle aged white guy.
It's not that it is an extremely terrible thing. If you know any of the backstory, you already know he is white.
To me, it's just that by this time, after 3 games and teases of showing his face, actually showing it just doesn't seem right. Everyone has their own idea of what he looks like. It should stay that way.
Also, I don't think Cortana is "dead". Maybe the Composer or the Librarian can salvage her in some sort of forerunner monitor device.
My only issue with this is that she gave her ultimate farewell already. Bringing her back after that just seems off to me. I'd like to see her come back, but I think they should have saved her rampancy for the end of the trilogy.
If they choose to go the whole MC dies in the end, which they need to eventually do, are they gonna have you find and resurrect Cortana only to have her die again?
I guess we'll see in the end.