I want to farm Act 1 for gear since Act 2 mobs just trash me. The end of Act 1 has some really rough elites though.
I need to farm more Butcher with 5 stacks of NV for gear, but my gear isn't safe enough to comfortably farm him and the elites leading up to him. Even with full health, his "instant" hook fan attack kills me 50% of the time (which I don't quite understand...I figure it would either always or never ohko me).
Last first - mobs just like you have a damage range on their attacks. So the low end of that range you survive, high end you don't.
There are a couple of ways you can go to beating him depending on how you want to play. If you want to survive a hit, try getting 3k armor and 300 resists with 20k hp (ideally you'll want more 30k+ when you can get there). That should keep you safe from being 1 shot (save maybe his charge). This, coupled with smokescreen will keep you safe from anything he can throw at you.
The above 3k/300 works well for surviving elites as well. Sure, early on you'll sacrifice dps for life. However once you get better at kiting and surviving you can replace your defensive with offensive gear.
As far as skill builds go and killing mobs:
Caltrops - Jagged Spikes (snare rune)
RoV - Stampede
SS - Lingering Fog
Prep - Backup Plan
Your Primary
Your Secondary
I say those specifically because it works well for the choke-point-laden areas leading up to Warden and Butcher. Basically you'll want to clear an area, then if you run into a champion or rare funnel them through a doorway. Lay Caltrops before, in, and after the door (don't overlap). When they hit the first of the three just unload on them. When they get to the doorway pop stampede in their face to knock them back allowing you to build up hatred and let disc regen for more traps or a possible SS. If you need more time to kill, just let them through the door and SS past them repeating those steps as they come at you from the other side of the door.
If you want to play a different way/build/gear then that's a different write-up