Sure,
Before I get into it, though, I'm gonna get into some boring philosophy stuff - a peak behind the curtain here. Whatever names I give you, it's important to take into account that all of Riot made this happen. Yeah, we had a small team that worked pretty hard on bringing this game to you, but without the guys over on the Skins team, we wouldn't have had the resources to make MvM. Without live balance, League would have fallen over a long time ago - they work to keep League fresh. Without the guys over on our platform team, we couldn't have kept League stable, and then we couldn't have made MvM. All the pieces are interconnected, and we had hundreds of internal playtesters that influenced the design pretty substantially. It feels off to celebrate our small team when Riot as a whole made the game. With that said, I recognize that as questions regarding gameplay come up, you'll want to chat with the Rioters who worked on this closely.
The initial design was done by Stone Librande as he was joining Riot almost 3 years back. The core of the game (stack programming) is still the same and all of that came from him.
From there, we brought the game in-house and had a handful of people working on it full time. For the first year and a half, it was basically me squared away in a closet trying my best (and failing) to improve upon the game. Eventually, we brought in Rick "Mr. Piddlesworth" Ernst to lead the design and create the ten scenarios. Nathan "FP McGee" Tiras and Prashant "Catspaw" Saraswat rounded out our core design team and I probably helped out on occasion.