Honestly, I hate how many effective free stats his passive gives. The champ won't ever be balanced until they fix double tap. I don't mind his escapabillity but when you look at his passive and really analyze it you instantly will easily find unnoticed stats that make him a bully early, middle, and late.
Right now I'd rate him as the first if not second best AD right near Yasuo mid lane.
Why?
Yasuo passive doubles crit on all attacks. Doesn't mean as much if you don't eventually build some AD. Free's him up to build AD items but he does have to get through an early game. His CC though provides an unmeasure aspect for comparison and his mobillity is more sickening which is the only reason I rate him above Lucian.
Lucian's passives, while they only apply to auto-attacks after an abillity, his abillities have a relatively short cooldown and because it applies to AA after an abillity he gets full effectiveness of his AD, crit, bonus crit damage,armor pen with his passive. Ultimately, there isn't a stat that doesn't work with it. Making this passive far superior to Yasuo. Effectively this passive provides similar damage output in the crit perspective but the fact that it measures in all other stats makes it vastly superior.
If that's not enough think about this, an extra attack with an extra chance to crit. Consider the following with an inf edge. Normally using an abillity on lucian i'm usually in auto attack range. Lets consider getting my normal AA and my passive double tap after an abillity with just an inf edge.
25% to crit the first AA
25% to crit the second AA from double tap
80-AD applies to both along with any of my existing AD/armor pen crit chance
Since each AA is 1/4 chance to crit you could expect this short AA sequence to crit once about every other time you use it.
Now consider the full lucian burst (minus ulti) that's 6 AA's with full benefits of any armor pen ,+80 damage to each, and on average you guarantee 1-2 crits each time you made this trade. Now I don't know the damage math 100% so this is just a guesstimate based on Infinity edge alone. But 80 * 6 = 480 + 90(bonus damage on 1.5 crits) = 570 / 2 = (235 effective bonus damage just from having double tap and inf edge. Doesn't seem like a whole lot? Now factor in all his other stats * 3 AA and add it to 235. You should see why this passive scales so well. TOO WELL to be considered balanced.
Until they do something similar to what they did to Kassadin's or Kogmaw's utlie.... preventing it from being spammed nonstop or in Lucian's case "such quick succession" he won't be balanced.