Life steal for Barbarians:
There are three ways to gain life by attacking monsters.
- Life on kill
- Life on hit
- % of damage converted to Life
Life on kill isn’t as good as the other two for barbarians. Imagine the scenario where you have 3 huge hitting guys on you that take away 20% of your life each hit, after 5 hits you are done if you haven’t killed one of them yet and then you don’t really get much health back.
If you had Life on hit or % of damage converted to life, every hit you deal you heal yourself again. So you would definitely survive more than 5 hits even if you haven’t killed one of the three at that point.
So that leaves us with on hit and life steal.
As I see it, you use on hit if you rather go the defensive way (which is in my experience the only way to survive inferno act 2 unless you got just incredible gear with dps and resistance stats) and if you use % based life leech you obviously want to do a lot of damage so that life leech really kicks in.
Edit: And as others have mentioned in their answers: your life leech gets reduced by 80% in inferno. So assuming you do 100k dps and had 10% life leech you would heal for 10k second before scaling down now if your life leech was only 20% as effective you end up with about 2k healed per second.
For on hit healing consider a fast weapon and frenzy so you get those heals incoming fast and steady. And no matter what dps you got, you get your promised heal for any hit you do.
For % I reckon it doesn't matter too much you either hit fast and get smaller heals or you slower with better heals. But your dps needs to be high or it won't suffice.
I myself will try a on hit build as soon as I find gear and a weapon that supports it and doesn't cost a billion gold a piece but the barbarian that has killed diablo on inferno did it with about 5k dps and roughly 1k heal on hit.
Barbarian solo, Diablo on Inferno difficulty