Tower Shot Attack Speed.
Let's face it, the game has reached a point in time where even a Janna can safely dive you under tower. My simple solution? Tower Attack Speed Bonuses. Don't fear, tanks and shields; the damage progressively gets weaker per tower.
It works like this: Outer Tower: 0% Bonus. 0% damage reduction. Inner Tower: 10% Bonus. 1% damage reduction. Inhibitor Tower: 15% Bonus. 2.5% damage reduction. Nexus Tower: 20% Bonus. 4% damage reduction.