Hm, maybe we should have some kind of tournament based around the harpoon. Just to see what teams can do when they actually (hopefully) try to make good use of it.
What would that accomplish?
I have actually tried to make good use of the harpoon. Other people have. In fact I would say anyone that has tried the harpoon even once has.
If a weapon is viable only in the hands of an elite few it's NOT a good weapon and most important it's awful design.
The situation is so clear that there is no need for further tests and proofs, the harpoon needs to be changed, period.
It's just that it's such a unique weapon in the game, not relying on direct damage at all; but instead creating a link between ships, pulling them together and making it difficult to fly.
I'm sure everyone has 'tried' the harpoon at some point, but I don't think anyone has put serious effort into it; actually attempting to make use of the weapon instead of just having it around for the achievement or chuckles. Doing it for the achievement isn't really trying to make good use of the weapon, since their trying to just make sure it hits before destroying the enemy as fast as possible, not caring about using the physics to their advantage.
No one takes it seriously. It's far from the easiest weapon to use, but that doesn't mean it's only effective in the hands of the elite. I think people just need to take more time to try and test ways to use it better, instead of asking for it to be changed because it's not used in the way they want it to be used.
A Harpoon-based tournament might encourage some of the more competitive to take time and test it out more, especially if it's use is required to win. It's no doubt a weapon that takes more crew coordination that other weapons. When do you use it? What ships do you hit with it? Where do you hit them with it? Can you use it so that their gun arcs stay off you or your ally longer? Can you use it so that your gun arcs are easier to keep on the enemy? Can you drag them into obstacles while avoiding those obstacles yourself?
A bad use of it might be sticking it on the front gun of a squid and harpooning the side of a galleon. Suddenly you're reeling yourself in right towards their guns. So you really do have to work with your crew, letting them know when to shoot and where to shoot; kind of like the flare gun: it's very situational, possibly being an advantage or disadvantage depending on how it's used.
Now if people do take it seriously and still can't make good use of it, then it might very well be an awful weapon. Needing to be changed or continued to be used for achievements only and occasions where players just want whacky all harpoon matches.