The thing that tilts me about Yasuo is his ease of CSing

Most midlaners either have to spend mana or put themselves at risk to CS.

I can deny Yasuo all I want early game. If I pick LeBlanc and zone him off CS, it doesn't matter - he CS's with near impunity, and it doesn't matter if he has 50 cs at 10 minutes, his ease of pushing and farming using zero resources and instant waveclear with no cooldowns ensures that even if he's 0/4 with 50 cs, he always, ALWAYS comes back into the game with 250-300 CS because he has the option to farm waves instantly and then join teamfights without having lost any mana or CDs. The second I leave lane to help my team, he is farming and healing back up with keystone mastery. For me to match him in CSing, I have to W the wave, hope they're lined up perfectly, Q to kill the casters, then slowly auto attack each individual melee minion, having to time it perfectly so the minions don't take the last hits.

Even with 40% CDR and morellonomicon, Lux, for example, has to E the wave, and auto attack each of the melee minions, and spend about 3-5 auto's on the siege minion. Yasuo just blows all his CDs, likely getting HP back from Warlord's Bloodlust, and is near guaranteed to get 100% cs with zero time or resources. If anyone comes up to try to stop him, windwall and dash away. Most other melee midlaners don't have the waveclear or safety that he has. Even Zed has to line up the minions perfectly, and he doesn't heal back from shuriken farming.

Not saying it's unfair, or he should be nerfed, but it's definitely the thing I find extremely frustrating about him.