Starkillers are the basic torps, they aren't meant to be good at anything compared with other torps/missiles. If you play Singleplayer, you'll notice you have to be something like rank 10 before you can use Starkillers, and rank 30 to use Sunslayers.
Its kinda like the difference between a Defender and a Guardian.
I agree with you on the mines though, but even if you make the other mines better, people will still use the strongest one available, since mines aren't limited to factions. But perhaps if we could make a variety of top class mines. Fast but weak, another could be slow but huge radius and great tracking, and then strong but cumbersome.
I'd like to see some flare mines too, be neat to set off a flash mine to blind your opponent cover your retreat, or maybe some crybabies, but I doubt that second one is possible.