lux is currently an okayish champion, she has good damage and is great in teamfights, but her passive does not suit her. as a champion who builds ap, lux does not have atk speed built into her kit, also her range is 550 which makes proccing her passive quite difficult at times. I personally would love to see a passive change but im unsure what it could be, any ideas? (also, zoe's passive is a better version of lux's passive) 
You aren't supposed to be able to reliably proc it. It actually accomplishes exactly what Riot wanted it to, which is force you to choose between extra damage or safety. Personally, I don't think it needs to be changed.
Also you spelled "the best" wrong ;3
wut…
Q, A, E, R, A gg
most of the time you don't even need to use the auto between q and e for her to pop someone. Lux has a great kit and the passive works very well although when thunderlords was a thing, it was op as HELL
Literally hit with a spell and auto for a proc on thunderlords. Doesn't happen like that anymore ( I really wish it did though)
Lux passive is totally fine helps with last hitting minions trading in lane and bursting people with your ult
