Pinsir really isn't supposed to resemble a fighting type, it's just because of his design that the can likely learn fighting type moves, (most pokemon can learn moves based on their design, like how water types obviously associate with water, so they can usually learn ice moves, or how dragon types are capable of learning fire moves, they don't fit the type description, but still hold characteristics of them.) As for the Gyrados being a dragon type, he originally was supposed to be a water/dragon type, but there weren't any good dragon moves in generation I, so they scrapped the idea...Imagine how much harder lance would have been if it was though. Dragon would be the only weakness it had, but there were no good dragon moves, you could barely damage a powerful sweeper.
