Mirror Mode is what League needed to freshen things up
Let me just start by saying I have always wanted to see a match where you could have ten Mundo's running around and never dying. I've found that Mirror Mode does much more than that, though. This is NOT just some fad that people will get bored of. On HA it plays sort of like an arcade game. Take Cass for example. Since there will be so much AoE going around, it becomes a game of positioning and patience, much different from League of Legends. I've never seen anything so close to a real chess match in League. And the amazing thing is, every champion that is applied to mirror mode creates a unique new arcade game on HA. So we have X amount of arcade games in one for all on HA, where X is the number of champions in the game. I wish I could have the time to explore all these wonderful arcade games, but knowing Riot's "we know better" philosophy, they will probably try to say it was a fad that would get boring when it actually is the farthest thing away from that. And then you have custom game potential. I played Yasuo one for all on SR, in a 3v3 where 1 person goes to each lane. It was truly an awesome experience, and I hope riot at least reads this and understands that mirror mode has limitless potential, and should not go away any time soon.