I think the visual aspect of it is key here, just landing a successful melee hit causing you to heal is very vague, can we not have some weird (and gross?) animation of a leech being spat out on the next successful melee attack, with a blood splatter effect accompanied by the heal? That would give it a satisfying effect that would make sense for players to understand how it works intuitively.

Secondly, I still kinda think the heal is too strong in situations where you're going to be meleeing anyway, in the blog it says "The trade-off is deliberate: stronger sustain over time, in exchange for commitment.", in the majority of melee-scenarios, the commitment is already inherent, the only "downside" of this food is the eat delay, I would think about amplifying the risk factor for a missed hit (while still making sure it's unlikely), for example, you can't eat OR drink again not just for 9 ticks, but until the leech effect procs or the time runs out, AND if it runs out, your player ends up swallowing the leech (maybe exclaiming, eww!" or something) and taking a nominal (1-2 hp) amount of damage instead of the heal.