It's cancer enough that we have to deal with high burst from them already. It's just a wonderful bukkake icing on the cake when we can't effectively itemize against their mixed damage..
(I for one hate corki, and if it wasn't for him being almost exclusively mid i'd throw more of a fit about him)
e46 Fanatic2 voteshonestly I wish they had more mixed damage adc champs. It might would just throw crit strike out of the window and make people prioritize real items and not just smacking op ass crits. Crit strike is the problem with marksmen :/
LatetotheRace1 votesI could get behind a solid compromise like that.
Eclairius2 votes80% 
's AA damage are magic.
his Q deal magic damage.
his W deal magic damage.
his E deal half magic, half physical.
His R deal magic.
It seem about 80% of corki's damage are magical, MR look like a good choice against him.
Also if a champ were more mixed (half magic & half physical), said champ wouldn't be able to build pen efficiently.