I personally think it will end up being best to just have all characters.
I have a 60 DH, Monk, Barb and Wizard.
My Wizard is my main which I don't bot on, my DH and Monk are my main bots at the moment, waiting for Demon Buddy to be on sale again then I'll start botting my Barbarian. Plan on making a Witch Doctor later too.
Currently my DH gets 440k/hr doing Core runs.
My Monk gets 420k/hr doing Sarkoth Runs.
However, my monk also ends up with a storage full of gems, rares and a few legendaries overnight. So overall, right now, my Monk is out performing my DH.
I'm pretty sure though that my DH with some better gear could be able to outperform my Monk though.
I guess it comes down to exactly what you're doing, if you were to eventually setup an Inferno MF bot, Monk would be better than DH.
Running a diff configuration for every bot would be a huge pain with every class. You cant say your monk out performs your dh because if the dh was doing the same thing i bet it would be beating it (assuming gear was equal)
This is why I think it is essential to have pretty much every class, eventually, something will be "overpowered" and it could be any class at any time.