How does life-steal work in the original Diablo?

I’ve been recently playing the original Diablo, since back when I was a kid I didn’t appreciate it as much as it deserved. Knowledge from later Diablo games helped a lot.

I have been having trouble with life-steal. I am playing a rogue and I’ve been using The Undead Crown which is dropped by the skeleton king.

The wiki says it gives me 5% life steal. At that time, my damage was ~5-10 so I assumed the 5% got rounded to zero. However, now that my damage is ~20-40. I still see no life gained from the crown.

My question is, how is the life-steal supposed to work? Is it only noticeable with really high damages? Is it broken?