General

active leecha aura -> hit monsters -> you heal -> if u need more heal, Use leecha arua again -> hit monsters -> heal -> repeating.
it doesn't need to wait 30 seconds cooldown for healing.

You activate it -> you heal -> you don't heal for 30 seconds -> 30 seconds later, you heal again

The cooldown activates everytime it heals you.

So the actual skill itself doesnt have a cooldown but the effects of the skill have a cooldown or intervals between each healing.

to put it simply, u gain life over time instead of atking like a madman and gaining 3% health from it. broken skill is a broken skill.