Essentia Sanguis, Mystic Harvest and Voracious

With Essentia Sanguis converting my life leech to energy shield leech, and the Amazon ascension node Mystic Harvest (elemental life leech), I expected the Voracious node to provide instantaneous chunks of energy shield recovery when doing massive damage. It appears Voracious is having no effect, as my energy shield leeching with and without Voracious happens as a continuous recovery rather than as chunks along with continuous recovery. Is this working as intended?

Maybe it's trying to apply 20% of the leech as life leech after it has already converted life leech to energy shield leech, so 20% of zero is zero? Given the wording of Voracious (doesn't specify what type of leech), I expected it to apply to the energy shield leech.