All of them. I believe they wouldn't allow one class to be the "best" for farming.
Idk... as much as Blizzard would like to have all classes be on a level playing field for all things, I just don't see this as a possibility. One or two classes will surely emerge as the best class to farm items and gold IMO.
I don't know about that. I mean, every class is going to have their upsides and downsides, but "best at farming" is such a broad, vague category it'll be hard to pin down a clear winner. It's only a little step down from asking "What's the best class in the game?"
In D2, basically two factors determined farming effectiveness: speed, and the ability to deal decent damage in inferior MF gear. With Teleport no longer being what it used to be, the two most mobile classes seem to be DH and Monk, but we can't say that for sure. Besides, we also have to take into consideration that farming in D3 isn't a matter of racing to the boss as quickly as possible, but hunting down all the champion rares before capping off with a boss kill.
As far as gear goes, D3 spells are designed so all classes are pretty much evenly dependent on gear for damage. Ultimately, I think the title "best farming" will be more determined by gear and skills than your class.