Just want to preface that I really enjoy the LoL events as a whole. I think they are a great way to not only meet more individuals from the community, find out what they like to play, how they play, etc, but also can really be a good tool to get feedback from other people on what they think they can do to improve.
Personally, I was not a fan of the structure of last nights LoL. It was an interesting concept and got a little hectic because of 30+ people showing up, but at the same time it led to some hurt feelings and less than interesting games. I can't speak for the other groups because I didn't play in them but in our group we had some people who were still new to the game (below level 30) playing with plats and diamonds as well as some lower ranks. While I'm all for people learning the game and would love to see more new guys in the community, I think in this setting that having those large gaps in experience tends to lead to a lot of frustration for the new guys as well as for the high ranked players. For instance, I'm a plat jungler and I would feel like a real jerk if I just kept abusing a new player, so my options are to be a jerk and try my best to win the game, or ignore them and not push our teams advantage to get the gold for killing them, or their tower, etc. We had a new guy to the community in our group who became extremely upset after our first game and refused to stick around for the second game because of this and I think others may have felt that same frustration but chose to stick around.
I know that this is not the usual setting for the LoL event, but if it is how we choose to run it like the last week of the month or however I predict we will see a massive decline in attendance for that particular week. Personally, I wouldn't want to come to an event either if I knew I was just going to get really frustrated. It takes away from the fun and the learning environment.
Again, this is just my opinion on the matter. Maybe I'm the only one who feels this way on the matter. Take it for what it is worth.