Quotes from the D3 Dev AMA

[Ashock]

You can believe what you want, but if you are melee, then w/o extensive use of the AH, you will be going nowhere past Act1 Inferno, if you are soloing.

How are hardcore people playing in Act 2 then? Yeah, they're using the AH, but they aren't using the AH like softcore people are (buying items from people in Act III/IV to prepare themselves for Act II).

They are playing there by not being melee. Besides, if you finish Act1 and enter act2, you are playing Act2. That does not mean you are progressing in Act2.
The first time I went through Act1, I died once in the whole act. In the same session, after killing Butch, I went to Act2 and immediately had several near deaths as soon as I left town in Act2 from just the dragonfly things right outside of town. I then proceeded to die twice to the first champ pack I met, and 5 times to the next.

Obviously, if I played HC, I'd been more careful, but this is just to illustrate the difference between acts 1 and 2 in inferno.