Riot, here's how you balance GP's barrels
Recently on the PBE boards Repetoir mentioned how Riot doesn't like how GP's barrels work right now.
Gangplank probably just shouldn't ignore Armor the way he does honestly. The Gangplank character on Live takes far fewer risks than he was originally intended to (I believe this is the case anyway) as players have learned to optimize barrel gameplay.
Well I have the best way to deal with that. Turn the armor pen on his barrels into armor reduction and reduce the percentage by at least half. By making his barrels shred armor, he needs to follow up on them to take advantage of that and it reduces his burst damage. Additionally it will give him some more team utility since it will help other AD champs deal more damage. So less solo burst damage and more delayed team helping damage.