Just saw both The Duel and The Babysitter.
It's interesting to see the way the Japanese put their style into this but I think some things made it noticably 'off' in the Halo universe. I'm not talking animation but persona. A Spartan wouldn't be mute throughout the entire mission like that nor would an ODST be THAT emo about shit. But all in all it was enjoyable.
I recently saw a dialogueless graphic novel "Breaking Quarantine" by Tsutomu Nihei which showcases Johnson escaping the clutches of the Flood, that style seemed to me much more loyal to the way this American series is concerned (aside from the Japanese characters used for sound effects; "GAGIGIGIGI" goes the assault rifle lol).
The Duel was pretty cool once you get used to the style. Though the whole jaw thing was rather stupid, you see in the games that the Sangheili speak with all four mandibles. But damn if that Arbiter wasn't of '300 Spartan' level...taking out a whole company by himself. And the 'final boss' dude confirmed my thought throughout the vid that this was definitely a samurai style