Life leech not working ?

After taking perks giving me "% attack damage leeched as life", I see absolutely no healing done with either default attack, double strike or splitting steel.

The weirdest part is that I did a similar build a few days ago and I remember it working with the same setup, however it was on Standart league and now I am on Crucible, which I don't think should make a difference.

Am I missing something ?

My guess is you aren't doing nearly enough damage for leech to have an effect yet.