It scales with AD at a 1:1 ratio, and works perfectly fine. Maybe the ratio is lower than it says it is.
No, it's a bug, His ult says it scales but it doesn't actually do more damage, it lies.
And his Q doesn't reduce 30% of armor, just base armor, so instead of 100 armor at the start it reduced you to 70, but if you have got a Thornmail his Q still reduced 30 of that so it's 170, only base armor is reduced. :/
Bugs