Arbiteeeeer :D
I loved him in canon anyway, and it's just so interesting to see him in a game and interacting with characters outside his canon and who are canon but not from the same time.
... Also is it horrible that I want him and Rookie to have the most awkward friendship ever?

I haven't seen much of O'Brien, but I can say I watched Halo: Legends because I was so interested, and I like him a lot. I hope to see more of him, and will enjoy Rookie picking on him :3