nvm, WW. What about
and his true damage E?
edit: The terminology and stack gains have been altered. A Takedown is a kill or assist. Currently Devourer grants 2 stacks for a takedown on a champ, and 1 stack for a large monster kill (not assists).
The new language reduces the champion takedown bonus to 1, increases epic monster takedowns (kills+assists) to 5, and 1 stack for takedowns (includes assists again) for large monsters.
It seems to me the new item will benefit greatly from killing Dragon because assists count.
As you know, WW is more than capable of taking Dragon solo at very early points in the game. Doing so with Devourer would benefit him greatly because +5 magic damage. Also, this mechanic would greatly benefit having multiple devourers on a team because everyone wielding a Devourer enchantment would get +5 stacks assuming they participated in the takedown.
The bonus damage on every other AA is kinda wonky. I really don't see why its like that.
In any event, I agree this is a huge buff to 
"Unique Passive - Phantom Hit: Every other basic attack will trigger a phantom attack that triggers all on hit effects a second time."
This is broken beyond all compare. Do you enjoy extra lifesteal? How about Jungle Nasus? His Q is an on-hit. Chunk? No, more like obliterate. HULK SMASH! What about other on-hits like
or
? How about
?