Yes, Static Shiv is a waste on Gangplank, because it is not that useful of a character. Of course, all the characters can do something, but Static Shiv doesn't have that much going for him. He is fast, but I prefer to use other characters that are more effective. Static Shiv is just a filler, because other characters are more powerful.
Static Shiv is a great minion/wave clearing item. Its crit, movement speed, and attack speed effects makes it a useful buy for Gangplank to use when he is chasing down an enemy champ. And because his Q applies on hit effects, static shiv can be used either as a long ranged minion snipe or strike every enemy champ in a teamfight so it is a useful item