Nothing against Keifer, but that's not a performance. He just did a few lines of dialogue and they plugged it into a character. It's good, but it feels somewhat alien in this game.
edit: I also find Troy Baker's Ocelot to be something else entirely. I can't believe this series ended on this stinker. People bash Kojima's long cinematics and goofy characters, but that was the only thing holding this series together for me. MGS5.. Fun gameplay (though bad open world), plot strewn inconsistently about that feels nothing like the rest of the games. I don't understand what this mess was supposed to be. It's all about the Motherbase stuff, but it's so mind boggling hollow. Am I supposed to care about these nothing soldier characters that stand around my empty and useless base, and I can't even take them on missions like in the other games? Apparently I am.