its a 3400 gold item which provides half benefits to anyone with who doesn't have both AP and AD scalings.
it gives 15% damage drain, reduced to 5% on ALL AOE abilities. ezreal has his Q,W and auto's to fully benefit from it.
This item suffers balancing issues due to it being far weaker on non-hybrid champs and too strong on hybrid champs. Ezreal is an hybrid champ so he takes full advantage from it.
despite that it will only provide healing IF you can provide damage, if you are say... CC'ed this item isn't doing jack shit. it doenst provide HP, or armor or MR and leaves whoever's rushing it open to Flat armor / MR pen.
its just ezreal's nature of long-range poke why it might seem to be out-draining an aatrox, or prehaps someone forgot to bring his
to cut his healing in half.
Ahri got benefit from this item due to it boosting her sustain: after the glacial + GLP combo this item became too inefficient to build and was left in the dust for those reasons. even new Morde avoids it, due to having no AD scaling on his abilities (and no longer having HP costs)
That's all.