Mid-Late game runes for an ADC

I take 15 AD, Marks and Quints on Lucian. It's enought to blow their ADC with AA>Q>Passive. Or just Q harass, which I can hit.

Problem is Irelias, Malphites... etc. Should I bring flat armor pen right off the bat? I'm figuring it won't take much untill they become useful, which is right at mid game start. What do you guys think? =P

Almost no damage to them with IE, Statik and BC. What is 35% armor reduction on a 500 armor malphite? lmao