Threats to Yasuo with this build
There are a lot of items you can get on Yasuo.
1. Phantom Dancer, Frozen mallet, Infinity Edge, BloodThirster, GuardianAngel and then your boots of choice. A bit tanky but still a lot of damage.
2. Statikk Shiv, Infinity Edge, BloodThirster, GuardianAngel, Maw and then your boots of choice. This gives you alot of damage, you will be very squishy though.
3. Phantom Dancer, Infinity Edge, BloodThirster, GuardianAngel, Ravenous Hydra then your boots of choice. I don't play with this item build much but it has pretty good lifesteal but not alot of survival abilities.
Boots: I recomend 3 types of boots, Ninja tabi, Berserker's Greaves or Mercury's Treads.
Try to ward as best as you can, you will get camped and if you are not ahead you can't 2v1.
Try to snowball the lane, you can do this in the early game when you hit level 2. Yasuo's level 2 is really good for an early kill, try to freeze it in the middle of the lane then once you are around 1 creep from level 2 try to move a bit back and let the other lane walk forward, once you are level 2 go all in. You will pretty much get atleast a SP every game if you could do that correctly.
Pros / Cons
Pretty good in 1v1's and teamfights
Can snowball really hard
Farming is pretty important for Yasuo, he need his items to be usefull in the late-game. Try to get atleast 80 cs every 10 min. If you are behind, farming is very important. Get the lane to push into your tower and just last hit.