[GAMEPLAY] No Health from Sion's W's passive

I have played two games in a row with Sion (a few weeks apart) and I've accrued no health from Sion's W's passive when killing minions or monsters. Current bonus listed is always 0, and total health does not increase. I've seen other Sions play without this problem, but have also seen other people report this. How to reproduce the issue:

1. Be in my account, I guess.
2. Select Sion.
3. Put point into W.
4. Kill minion.
5. See no health increase. Thanks!