Resistance and Vitality

I have built absolutely no resistance or vitality into my sorcerer build. I have been putting most of my points into intelligence (I just reached SL100 and I have 87 intelligence), which has turned me into a killing machine. Unfortunately, though, I die in a few hits to any type of enemy. I was having a lot of trouble earlier fighting Nito for this reason (because of his skeletons). How big of a difference does resistance and vitality make in terms of taking a few hits? Also, how many points is a good amount to invest in them?