Siphoning Attacks tool tip says:
Imbue your weapons with soul-stealing power. For 15 seconds each basic attack restores 927 Magicka and 972 Stamina. All non-basic attacks have a 10% chance of restoring an additional 1944 Magicka and Stamina.
However, sometimes when doing light attacks, I see no stamina restored. I used up most of my stamina sprinting and dodge rolling and then just light attacked a monster with siphoning attacks on and a few of the hits returned no stamina.
Is this a bug?