I just soloed my way through the rest of Inferno Act 2, mainly to prove to myself that it could be done.
I've decided that the real reason Act 2 is so much harder isn't really because the mobs do more damage (although they do, clearly). It's because Act 2 ratchets up the prevalence of Don't Stand There Damage. Blizzard's always been a fan of this (see: every raid boss in WoW that had a "dodge or die" mechanic), and while it's not necessarily instant death in Diablo III, it's still far more damaging than normal melee hits. There's a bit of it in Act 1 (molten/desecrator packs), but in Act 2, you start seeing normal mobs that have it as part of their base mechanic (the small demons that explode into poison clouds on death, the Blazing Constructs that attack with puddles of fire). Act 2 just requires a whole lot more motion out of your character to avoid the DSTD, and the elite packs of mobs that feature it to begin with (like the Frozen/Waller/Extra Health/Fast pack of Blazing Constructs that I ran into today) are pure murder. Once they CC you in their DSTD, it's curtains.
I managed to kill every pack that I ran into, but there were a couple that probably killed me a half dozen times a piece. Still, I made money over the course of the run (from Kulle's blood through Belial), and my NV stacks never fell off.
My gear's not exquisite or anything, although I will admit that my weapon (which I purchased in the first week of the RMAH for cheap) would probably be worth significantly more than I payed for it now.My Character Sheet (Unbuffed Numbers)
 - Actually, I see a nearly identical weapon on the AH for only 2.5M. That's not too bad.