From d3cab.org:

Dear Diablo III Development Team,

This is a message on behalf of the portion of the community that engages in the competitive aspects (such as Leaderboards and Conquests) of this game you created - the players who love the game to the point where they dedicate large portions of their free time to playing it; who want to have at least something to show for this dedication; who want to have their names up there on the Leaderboards; and who want to see rewards for the countless hours of gameplay they spend on Diablo III.

You’re making this incredibly difficult for us.

We all know that beating the highest possible Greater Rift tiers requires a large number of attempts in addition to the time investment that is needed to get the appropriate gear. This involves a lot of grinding, be it for Keystones, crafting materials, Infernal Machines, or Ancient Legendaries. Such is the nature of the game and that is not the issue. The actual problem lies in the vast amount of people who try to get around doing this dirty work - the ones that use bots; the ones that can log into the game to hundreds of Greater Rift Keystones, Legendary crafting materials, or Infernal Machines every day, without having lifted a finger for any of those. It should be obvious that this provides these players with a huge advantage over those of us that choose not to bot, but put at least the same amount of effort into the game and advancement of our characters. This feeling is extremely disheartening. We all know that it is incredibly hard to beat the botters and even impossible if they were to step up their gameplay to a higher level of efficiency. They can get a huge lead on you every single night. This knowledge reduces the incentive and desire to participate in the Leaderboard competition until eventually the Diablo III competition becomes a farce altogether. Thus, those of us that love the game and have been dedicated players since the start become increasingly frustrated with it until we simply give up on the entire competition, or create our own, virtual “bot-free” competition by ignoring all known botters.

To prevent that, your very own End User License Agreement, which we all agreed to, states that players may not use bots such as these, even giving “the automated control of a character in a Game” as an example for such a prohibited program (Section 1.C.ii.2. of Battle.net® End User License Agreement, http://us.blizzard.com/en-us/company/legal/eula.html). Enforcing this agreement is your duty and yours alone. If you don’t, it will only go to show that you don’t care. It has been months since the last major action taken against botters and, consequently, Season 3 was dominated by them. Our friends lists contain more and more people who are online for more than 20 hours a day, despite them having to go to work or school. Even if detecting the actual bots running on people's machines or identifying them by their in-game behavior was impossible, their log-in times should be more than enough to warrant additional investigation. Nobody can play for 23 hours every single day.

Even if that were infeasible, at least let us report botters so that you may investigate their behavior. It has come to a point where it is quite obvious that certain high profile streamers are botting off-stream and some are even admitting so themselves in public chat rooms. These players are viewed as examples by the community, so what kind of message does that send? To us, it sends the message that not only is it apparently legal to bot, but that the game even requires it to be competitive. That is undoubtedly not how you want Diablo III to be seen, especially with how far we’ve come since the issues of the original release.

Of course, we would prefer any action against botters to happen immediately upon them being discovered. However, we are aware that this is likely infeasible. Thus, we would propose any action against botters to take place approximately two weeks before the end of a Season, coinciding with the “Season Ending” announcement, as to not give botters the time to catch up to the legitimate and fair players again. The latter would then still be able to fight for the clean Leaderboards, as they would if botters didn’t exist.

Still, with no action having been taken for so long, sending out a message to the entire community sooner rather than later would be a good idea.

Please, if you have the same love for the game that we do, do something about the botters. It cannot continue like this. We cannot continue like this.

Signatories (in alphabetical order):
Alkaizer, Angzt, Anuiran, Bagstone, DatModz, DameVenusia, Deadset, Destitute, Empyrian, Flux, Ghostwheel, HolyKnight3000, HorstSchlemmer, Jaetch, Leviathan, Lt. Lunatic, MannerCookie, MeatHeadMikhail, Menagese, N3rdwards, Nachten, Natsuma_z, Neinball, Quin69, Thunderclaww, Wudijo, Zero(pS)