Doran's / Tough skin fix?

Doran's shield

Reduce the damage taken (post mitigation) from champion basic attacks by 1 for every 100 units between you and the attacker. Doubled for melee champions taking damage from ranged champions. Your basic attacks against enemy champions disable this passive for 2 seconds.

Seems pretty simple to me, if Cait hits you from 500 range, you take 10 less damage as a melee champion, 5 if you are ranged. If you engage on someone, your defenses are penalized. If you engage and the enemy adc kites well, your defenses are still compromised briefly.