Tank IDENTITY

[DannyDeDitto]

As vatom said Lifesteal is, by all intents and purposes, life per hit, but also life on kill. Many other games have their own way of building it;

GW2: Is a separate proc that deals a flat amount of damage and heals a flat amount of HP, and they're scaled separately from Power and Healing Power.
Path of Exile: Heals from damage dealt, but applies it as a regeneration effect (unless you have a certain unique equipped)
WoW: DKs have Death Strike, which heals you a flat 10% of your HP and more scaled from the damage you took recently, granted there is also a leech stat from other means and that one is the simple heal from a perecentage of damage dealt
Castlevania SOTN: You had Dark Metamorphosis which healed Alucard a flat 8 HP from each blood sprite that collides with his body.
Dark Souls: Some items like the Server and the Butcher Knife would heal you (a miserable 5 HP) on hit, there was also the Ring of the Evil Eye which healed you from each kill.
I don't play LoL but i remember Vladimir is a vampire and heals from his Q which is a ranged attack, from what i read that's also just a flat amount of HP.

I could mention more but those are the ones i remember atm. Personaly i always prefer the heals from damage dealt version as that one feels the coolest but all lifesteals are nice, i think it has a bit more to do with the theme, cuz i remember some games that also add heals from damage to holy boys and girls, and i wouldn't really call that ''lifestealing'' since lifestealing is like i said before, more grim in nature.