Lucian, while possible to bring mid lane, isn't a good mid lane champion.
Reasons:
-He is very squishy
-He has low auto-attack range
-His burst is mediocre compared to many other champs
-He is AD (thus possibly removing an AP champ from your comp by bringing him mid)
-He has no CC to contribute to the team, making him practically useless if he fails laning phase
-His best build items are ADC items
-His only escape/engage is a long cool-down, short ranged, dash
-There are better choices for midlane marksmen that actually are proven to work well (Corki or Varus being the best examples)
Pretty much, if you pick Lucian mid, you will have another AD champion (potentially causing your team to have a full AD teamcomp), who is less effective than Corki or Varus, less safe than most mid lane champs, has less burst than most mid lane champs (especially another AD champ like Talon or Zed), who has no CC or reliable poke to provide the team, and who has to play as an ADC anyways during teamfights, but without having the benefits of an ADC's damage output.
In essence, he is a tier 3 pick (out of God Tier, Tier 1, Tier 2, Tier 3, and Tier 4), bordering tier 4. Viable, but the challenge does not meet the reward of playing him; choosing another champ could provide much more with less hassle.