Kayn Rhaast Passive Problems

Okay, so I'm having a problem where I will choose the Rhaast form for Kayn, yknow so I can cc and tank and the like for the team, but all the damage I do doesn't heal me at all.

There was no involved to reduce healing and I even had to increase the healing I got back, but I still didn't get any healing from my damage. Is it just because my damage was so low that the healing from it was miniscule?

This was my build: BC > Merc Treads > Visage > Duskblade > Steraks

Please help me understand what's going on because from what I remember I used to get healing back from the damage I dealt as Rhaast, but now It doesn't feel like it at all.