I'd say up them resists and drop the health if needed. I remember pre-1.0.3 when I first hit Act 2 I was wiping constantly, then just played the AH to up my gear got to around 800-900 resist and was able to take a lot more. But then I dropped resists for dps in Act 3. But I'd say about 400+ should be sufficient enough if you can kite/play smart.
Life on hit is awesome....but really expensive. On my barb I found that i could get good vit/resist all gear with Life regen. for alot cheaper than life on hit. My life regen is 1300 and it is a huge help. With the attack speed nerf I figured life on hit would be a little less useful, so i checked on life regen and got it basicly free on my vit/resist all gear!