[ADC Item Concept] Hextech Shotgun

I basically want an item added in the game that allows ADCs to deal with tanks.

Hextech Shotgun (Ranged Only) 40 Attack Damage 50% Attack Speed (100% lifesteal on passive)

Unique Active: Upon activation enemy champions will receive 10% of the health difference between you and them in true damage every auto attack for 15 seconds. (30 second cool down after duration ends) (reduced cool down per kill/assist 5 seconds)