I was playing Aatrox jg and noticed that once you get full stacks on devourer his W was not triggering every two attacks. It sometimes would, but mostly you could attack and it would not trigger at all. As if the counter was somehow skipping over the 3rd attack and staying on two.
It's not bugged and functions exactly as it's supposed to. The reason you think it's bugged is because it only plays the W animation if you have the W buff ready at the start of your auto. But regardless of whether or not the W animation plays, you are getting the extra healing or damage every 2nd hit.
I've actually noticed this as well, and I've figured out why. It's because Riot doesn't care about Aatrox at all. With sated devourer, Aatrox's w procs after only 2 auto's , but riot has ignored him for so long that they haven't even updated his animation to work every 2 auto's instead of 3 after buying sated.
RIP Aatrox 
Aatrox's W procs on every third strike similar to how Xin Zhao's battle cry crit procs on the third strike.
In order to get the phantom hit for his W it would have to sync up with the third strike, meaning that you only get the phantom hit benefit for W every 6 strikes.
I don't know if it is intentional, but that is how it works right now.
yup, bugs everywhere, dont know if it happenend to you but sometimes (only happened on the new skin) after landing with Q you turn invisible and all you can see is your sword, and so will the enemy
