As a pure intellectual matter, I think this is going at the wrong direction. So I will try another approach. I will post my reasons and leave it at that.
Long Range vs Rush
Short range weapon will always have more DPS than long range ones if the game is to remain balanced. Therefore, going short range is an all or nothing approach. If a rush is successful, then Short Range wins, if a rush is unsuccessful, then long range wins.
3 long range weapons that has any hope of stopping a rush is Fast Missile, Rockets, and Beams (normal or fusion). Plasma is usually way too slow for this purpose.
Rush
In regard to short range, 4 weapons in particular stands out; Ion Cannon, Howitzer, Rad Gun, and Cruiser Laser.
Ion Cannon yields the most DPS for the cost. Also comes with most speed and EMP. Their biggest weakness is frigate’s low shield resistance. As such, decoys are always needed to let them get close. On maps with the right credit/pilot ratio (such as RCIX-SAC), these puppies can really dominate.
Howitzer has the lowest DPS for it’s cost. It’s advantage comes in speed and HP. Howitzer ships can reach over 0.4 speed, allowing it to rush through most long range with ease. The sacrifice of DPS for speed makes them the loser in short range to short range combat.
Rad Gun is the slowest bunny, worst in a rush, but it eats tribes (and therefore howitzer) for breakfast. It’s superior tracking also make them good against Frigate Spam.
Cruiser Laser is the second slowest bunny. It has less rush capability than a Howitzer, but can beat howitzer and rad gun in close combat. Their low tracking make them particularly weak against frigate spams however.
Conclusion
Most challenges are not rush proof, be it CL, Frigate or Howitzer. CL, while easier to use, is not particularly overpowered compare to the other rush weapons. All of them are fully capable of winning against many balanced fleets. But all are far from indestructible once posted. As I always said, the advantage is always on the challenger’s side.