Corki needs more buffs.
I dont really play adc so I am not here to judge his last buff and how big of an impact it is.
However according to a lot of stats from lolking, op.gg, champion.gg -
Corki's winrate has only increased by 0.6% after the buff. His winrate is still only 46.5%
He needs more buffs.
IMO, corki was a poke champ and fits into AD heavy comps and poke comps, the nerfs on his ulti's base damage was the reason why he is seeing much less success, his ult isnt doing any damage late game.