lux has very good ratio and very strong abilities.. but she is also immobilt VERY squishy with VERY long cooldowns on her primary skills.
the reason lux rushes to 45% CDR is becuase of the long cooldowns.
if lux actaully misses a Q or an E your and VERY easily trade her. and while her passive is VERY good it also requires her to be MUCH closer than she would need to go just to land her skills.
lux has counterplay
if you can dodge the Q you should be able to take her down easily.. she has no escape with her snare the only thing keeping you at a distance if you can bait that out or close the distance after it hits you she will go down very fast. also keep in mind her snare in not a stun or a silence.. you can still attack back.
she she strong? yes she is be she dones't have an escape and she is squishy, if you can close the gap you wont have much trouble