Courage of the Colossus

So, this mastery on champions like Dianna, Jax, Trundle, ect Gives them such a large shield that a Dianna could legitimately 2v5 dive a tower, missing her q twice, and getting stunned, because of the shield hp. The percentages need to be nerfed, because people are already abusing this on burst champs that have the tiniest amounts of cc.