what's with all the spam? do you not know how to look at stickies? you've asked this question in nearly every class forum and in the HC forum. why dont you research things a little.
Well look up the guides in all 3 forums and find the one you like the most.
Im guessing fire druid would be best for hc but other people have better advice than me about that since I do not play hc.
Depends on your preference. Look through the guides and find a build that you think you'd like to play. We can then, if it's not done in the guide, help you tweak it to be HC friendly.
Safety first, so something that has minimum chance to get hit by evil things while killing quite fast, or without major difficulties (in hell). And has big life pool. Look through skill trees with above glasses on and therein lies the key to build(s).