So I'm playing xerath
and enemy yasuo 
constantly puts up windwall.
I charge up the pulse with a different charge distance each time and it still phases through.
Not sure if that is supposed to happen but I know windwall would block a lux ult beam so why is arcanopulse still passing through?
Windwall doesn't block Lux's Final Spark so I don't know where you got that bit of information. The reason it didn't block your Arcanopulse is because it's not a projectile. It doesn't travel from point A to point B, it's an instant line. The same with Lux's Final Spark, or any other abilities that are instant line. In addition, it doesn't block over head projectiles, meaning things coming from above the wall. Xerath and Zigg's ult are examples of this.
Not a bug, just here to confirm what the first reply said. Windwall really doesn't need any buffs either
Windwall won't block a Lux Ult. It won't block anything from Xerath other than his stun. It won't block a Viktor's Q empowered auto-attack. These things are not projectiles.
Windwall blocks projectiles, not instant-casted spells like Lux laser, or Xerath's Q.
Doesn't block arcano pulse or final spark. Only thing of xerath's it blocks is his E
