Act-1 is a piece of cake if you know what you're doing. I can solo it in my 105 percent MF (without NV) gear now, and my gear is pretty average.
Only speaking for Barbs here, but I think too many of them fall into the high DPS trap.
You don't need more than 7k DPS for anything in Act-1 and this includes the Butcher.
What you do need is atleast 30k HP, all resistances at 300 (450 after the Impunity buff) and 7k armor.
If you meet those requirements, nothing can kill you in Act-1 if you chose your skills well and use them correctly.
The only elites that will give you a problem are Dark Berserkers as those hit really hard if you don't learn to dodge their backhand swings (run away in a straight line, don't try to circle around as they will rotate 180d mid-swing and hit you anyway ).
Basically wat he said. Act 2 is when things start to get really tough and you start encountering really frustrating elites The shielding ones are the worst in my opinion. Even my barbarian with 50k hp, 17k dps and AR 700-800(buffed with warcry) dies a couple of times in an Act 2 run but most of it otherwise is fine with those stats.