@Riot if you really want to nerf Gangplank
Then remove the movement speed he gets from destroying a barrel, on a champion whose main weakness should be immobility he has 3 somewhat powerful movement speed steroids (4 if you count Phage procs) and a W that heals and cleanses CC, Gangplank simply has a broken kit with insane damage and global presence and... actually everything you would want in a champion, you should at least get rid of one of the movespeed boost on destroying his E so he has to take risks to get his true damage off.