I've made and been messing with an excel sheet. Using Draven stats at level 18 with 17/13/0 masteries and pen marks and quints. From my numbers, talking pure aa damage (my model isn't intricate enough for abilities yet), Adding IE (or a second IE even) always does more damage than adding LW or BC.

I'm taking care to watch for uniqueness of the critical damage modifier and everything... Yet it seems no matter what that if you can afford IE you should always purchase it over penetration.(until you hit 100 critical chance)

So for top damage of aa I've got:

Berserk boots, bt, pd, ie, ie, pd (2nd pd turns out to be marginally more dps than a 3rd ie)

Technically ie should be before everything, but I like bt and pd first. I've gotten the same results from 40 Armor up to 250.

Thoughts?

2nd IE? I feel if they have 150 armor + you should be getting last whisper instead.

Um. Two IEs.

i'd understand another bt but 2 ies is stupid

doesnt crit cap?

*gets stunned, dies to the Pantheon with only two offensive items*

Well of course buying defensive items is smart. I'm saying from an offensive stand point ie (and yes a second for the ad and crit) is always better than an Armor pen item.

The build I posted is what my sheet says would be maximum aa damage. I wouldn't literally build that in a match.