I designed a parasite 1,000 ton gunboat with captured Precursor components, for the purpose of dealing with a race with exclusively fast parasite beam ships. It outranged the enemy, the fire control was rather inaccurate at that range, but since it was faster it would just plink away at the shorter ranged enemy. A single ship killed over 20 times its mass of the enemy.
I also used it to run down enemy missile ships that had used up their load, as it could easily stay out of range of their point defense lasers. It was a specialized pursuit ship, and the goal was that every important fleet would have at least one of them.
My fighters tend to be somewhat longer ranged and endurance than is strictly optimal since they evolved out of using fighters as jump scouts. And my carriers evolved from being long endurance barges that supported survey efforts, so my preferred launch distance was from the Jump Point.
A magnetic fusion beam ship should be a LOT faster than 10,000 km/s, in my opinion.