Can we buff Fizz's passive damage reduction?

Can we buff it to be percentage-based? It doesn't seem useful at ALL late game. 14 damage is about 7 - 8% reduction from non-AD champs; it's less than 5% for full ADC's and about 6% for AD casters (rough estimates).

It just doesn't seem useful besides the ghosting part; Ninja tabi does about double this for only 1100 gold (1200?). Right now it's 4/6/8/10/12/14 damage; can we buff it to 5/6/7/8/9/10 percent? Or something like that. Or change his passive completely; it seems a bit outdated relative to his brand-new rework.