I have created the most glorious revolution in anti-Yasuo/crit dps technology

Feast your eyes upon it. During defensive curl, Rammus will have 624.5 armor (Not counting bonus % from masteries or the flat increase from runes), and a 50% crit damage reduction. Mobility in the form of his Q, and a taunt that makes people kill themselves on this nearly impervious (to non APs) megaball of rolling near invincible anti-crit doom.

Even Vaynes will not be able to 1v1 you in the lategame, as she'll die from attacking you before you die of true damage.