I figured I had to comment on this, because of the recent changes : Lux's passive didntdid not scale on AP until the last patch, when they reduced the scaling per level and introduced a 20% AP scale. For most AP Lux players, it is a boost to her dmg. I had calculated her burst combo before the patch to be among the worst of APCs (about 200% on her combo) but her base dmg is one of the best if you can get 3 passive procs (Q-AA-E-R-AA), but you don't get that kind of opportunity very often. Now you can add the 20%, or 40 or 60 if you can get the autos.
Before the change, the weak AP scaling (Compared to other standard APCs) meant you had to prioritize Magic Penetration and CDR over AP. Now, I guess you can consider trading some of the CDR and/or Magic Pen for some more AP.
For the AD question, I'd say that this is something really hard to theorycraft, because it is completely based on the number of autos you can get on target, which depends on the enemy champion, the situation, and people would think a good estimate is your range, but this is wrong because you have a snare spell, if you didn't have it, Lux would be less of a threat and it would be more difficult to get free autos.
You have to test it ! Be creative, like Siv HD's Counter-Bruiser Bruiser Lux ("She's impossible to counter : Becuase she has everything")
AFAIC, I wouldn't find building AD or trying hurricane multi-proc tricks on Lux a viable option. But I have met good Lux players that can get the most of her by building AP/tanky items to allow her to survive long chases and escape with her slows and snares. Try it !