do you know why the standard for him is rush shiv?
its because early game BASE AD is king, no1 has had time to build armor (mid lane), so you're effectively dealing double damage on every auto. which lets say you only have 70 base AD by the time you complete shiv? (its more like 95~105 ish with a dorans blade and runes) and now you have 40% crit chance just because of his passive.
- all of your base damages on abilities.
so its "like" having more than 70 AD on your INCREDIBLY CHEAP, + GOLD BONUS item while building. you also get its +magic damage effect and the movespeed which is quite nice (when finished). and the wave clearing that would otherwise be a problem unless he puts himself in the wave.
granted he doesn't always crit 100% of the time with just shiv, but you get enough autos off and its more meaningful in the early game than any other rush item on another champion. its like "i got shiv, i hit a huge powerspike for no reason!"
if yasuo were to dive, use all of his abilities once, and maybe 2 auto attacks, it would be unheared of for him not to get at least 1 crit, and have dealt enough damage to 100-0 you, which is fairly normal for a lot of mid laners, but his item is cheaper and grants him waveclear, and safety/chase with that MS.
its not like he fails to 100-0 you 60% of the time when he doesn't crit, but ya know..... those super short CD's of his, he'll just try again in another ~15seconds.