galz has a point, you can improve your mitigation by at least a factor of 10. And how much life regen on top of that? How big a health pool? Those are subjective but let's say you have enough passive regen to gain a fifth of your globe per second. Needs somewhat optimal gear rolls, but the DPS that, say, a single arcane sentry or the damage of two overlapped ice explosions IS tankable once you get the proper gear.
With everyone so focused on living in inferno so early on, of course it won't be survivable. How many of these people have optimal gear? Not a one, since the RMAH hasn't been turned on. The moment the RMAH goes live, we will have someone demo for us. Inferno IS playable. Blizz just set the progression curve very steep, and everyone has their sights set too high. Farm hell for a week or two, get yourself 1mil EHP with a 50k health globe and 5k regen/sec. Then we'll talk.