Gankplanks q is bugged

Gangplank's Q is an ability that applies on-hit effects, so while it is a spell, it is treated similar to a basic attack as well. This means that it will aggro minions like a basic attack does and it can be dodged by Shen's W and Jax's W. it can also be blocked by Pantheon's passive.

This is all intended, and other abilities that apply on-hit effects are treated the same way.