Your whole system, ranging from reporting to voting in tribunal only encourages more hate, more reports and more bans. The bans will eventually create a loss of revenue because players will either find a new game to play during downtime or stop paying for skins and champs knowing they will eventually lose access to their account. Furthermore the reasons for banning are murky and its debatable that many players are either unsure why they get banned or flat out did not "really" deserve it. At the very best, you are in a destructive system promoting vengeance and retribution and thats never good. Not to mention the players who play more are currently at higher risk to get banned.
The solution in 2 steps:
1-Get rid of tribunal and reporting system.
2-Add a voting system at the end of each games.
How it works:
After each game, every player is forced to give a +1, +0 or -1 reputation rating to each teammates and opponents before moving on to the next game.
Each players who played well and/or had good behavior can be given +1.
Each players who had a bad game or attitude, whether because they fed, sucked, left, trashed talked, etc. can be given a -1.
If you are neutral towards a player, you can give +0.
Riot can then add coded rules where if a player vote the same thing too many times in a row he gets -1 for each subsequent vote. this to help reduce the amount of immature players or lazy players giving the same rating to everyone.
Let the law of average sort things out.
If a player is nice and skilled in 10 games, he should mostly get +1s. He may get occasional -1s from an immature player but overall his average will go up.
On the other hand, the player who thinks he is godly because he sits in bush during whole teamfight and chase weak enemies after the fight to have good K : D ratios will be voted down often and as such, will see his average go down even although he ends with good results. The players with overall poor attitude will be voted down and see their average get worse by the day. At the end of the day, those are the players contributing to making the game less fun and although lots of them are caught in the tribunal, lots of them get away while the tribunal bans other occasional offenders.
You can at anytime work towards changing your behaviour to improve your reputation. If a player finds his rep too low to getback up they may opt to make a new account instead which would be a similar outcome as a ban in the current system.
Ok so you got reputation, how do you use it?:
Now that you have a measure on how bad or good players are, you have a tool to work towards rebuilding your game to a healthy state.
There are various options available to Riot at this point and here are the ones I can think of right off the bat:
1-You can build a new matchmaking rule where players will be matched with other players of similar reputation. Create brackets of say -100 to 100....100 to 500 and -100 to -500 etc and pair players in games based on this. it would be a similar system as the ELO system where ideally, the higher in rep you go, the better the overall game quality you should encounter. You can early combine this with the ELO rating.
2- Introduce a reward program. This is the big one really right here. You reach 100 rep? get a new skin out of bracket X. reach 300? Get one fronm bracket B. Reach 500? get a champ from bracket A. reach 1000? Get a free champ from bracket B. Reach 10000? Get a tshirt? Maybe the player with highest rep can have a trip to Riot at end of year. Anyways...you get the point. these would be for Riot to assess. I would suggest resetting the rep to 0 every year or so but again the whole system/reward program would be evaluated by Riot.
How is this a better system?
It may not be a flawless system but it is a much superior system to the one we currently have with the tribunal and reporting system. The current system promotes hate, vengeance and retribution. It may reduce the incidents by a small percentage but does nothing to encourage players to have fun, be nice and get better. You are fighting fire with fire right now and that is never efficient.
My system on the other hand creates responsibility, accountability in a fun and positive environment. Heck its a game within a game. You are now working on building your rep to get goodies...same system that kept people hooked on WoW for years.
Adding a reward program helps reward your regular players and the ones who show good behaviour a high percentage of the time.
The tribunal may ban you because you showed bad behaviour 10 times in the last month. But what is 10 times out 100 games for a player and 10 times out of 20 games for another? Why are they both affected by the same punishment? Its not fair. The proposed system will help correct these inconsistencies. We are all humans playing a competitive game and will occasionally slip and its ok so long as it does not become a habit.
To give further incentive to not continue down the bad reputation lane, you would have an automatic punishment system when you reach specific ranks of negative reputation. Warnings, suspensions, bans, etc.
What else would help complete this positive experience?:
Because a huge source of frustration leading to bans is the varying skill levels of players (The proof is all the elo hell posts), it would be crucial for Riot to add more information/ressources within the game interface to help players improve.
Instead of asking everyone to go work on your trbunal you can ask a few of the elite players to help you create videos showing the basics of the game to players. For instance, where to place wards, when to do it, how to jungle, how to deal with good and bad laning phases. Show examples of good and bad team fights and why. Show how to push a lane. Show How to properly mid.
Concerns that were expressed with answer:
This system would punish poor play.
The tribunal already does this (unskilled player, feeder report options). The difference here is if 9 out of 10 of your game your team feel you cost the game, then your rep will go down. If you played 100 games in a week and had terrible games 5 times, you wont see a dent in your rep. the tribunal system on other hand will potentially have 5 reports for you and you may be banned as a result because lets face it, when you see 5 complaints in a week, you wont assess how many games he played...you will just see terrible records 5 times and vote to ban because it seems like the obvious thing to do. My system prevents unnecessary bans.
This system would add more rules to matchmaking and create longer queues.
Good point. This may or may not be feasible but consider this:
-Lots of requests on boards to pay to play with age group of 21+ (really people are asking to play with the people in my system who would have good reputation)
-If people buy in the system, it is likely only a small percentage of players will end up being ranked down due to their uncontrolled behaviors or complete and consistent lack of skills, whether on purpose or not. This said, this group would be likely to see their queue timers go up. So what does it mean? good players still have good queue times, perhaps a few sec even a minute longer but wont have as many games ruined by a bad player which means they save many more minutes in the long run. Bad players would wait longer to play...isnt that a good little reason to start being nicer or leave (same as getting banned several times)