Piranha are truly excellent as long as you give them a little escort. Even if you don't, two to three massed wings have enough swarmer firepower to ward off most ships.
The Broadsword is (at least imo) a complete waste of space. If you are going to spend 6 points on a ship to take down shields, go with a wolf or Tempest if you have the cash. They are far more capable and the Tempest is faster to boot. If you want them as interceptors, buy some wasps. Oh, and if you field either don't go up against the tri-tachs unless you have plenty of other PD ships - wasps will eat either for breakfast.