Did Gangplank really deserve a nerf?

Yeah it kinda was :/

He melted tanks in around 2 seconds

I think riot imagined gangplank strategically placing barrels before fights began, so that you could play around them skillfully. But what ended up happening was gangplank would stand back and throw 2 barrels down and q the first one as poke (massive poke). Riot probably wants to encourage people to use barrels less as a poking mechanism, and more as something to team fight around, requiring specific strategies and foresight. Just my guess as to why they made the change.

nope