Cast on Critial/Arc Blood Mage Leech possible bug

I am using Spark to proc Cast on Crit (which is socketed with 2 Arc skill gems). When I fight a boss and Cast on Crit procs, it sends arc to the boss many times, i'm not sure if Arc can chain back to the player or not. Anyway my issue is that I am not leeching life from the Arc chains. I am playing a blood mage with the 10% leech node and using Atziri's Acuity for instant leech. I'm under the impression that I should be leeching my life back from when the Arc chains hit the boss (I have 100% crit hit chance). Any info about this would be greatly appreciate. It's possible that chains from Arc are not supposed to leech life? I would just like some clarification. I know GGG is swamped and this isn't a major issue. I appreciate it and I think the game is great and I am having an absolute blast. Thank you!!!