Just to make sure I was accurately remembering, I went into the sim and tried to shoot down frigates with the Hurricane. Even if the target is overloaded it usually misses with half its payload and then the target survives because the reload time and flight time are so long. The Hurricane, is not a "large Harpoon".
As far as "the same weapon in multiple sizes" being a bad thing.... no? Ballistic slots literally do this. A railgun upgrades to a hypervelocity driver, upgrades to a gauss cannon. They do approximately the same thing, they work the same way, just more damage and longer range. Or if you prefer something more shotgun-like, there's Needlers for all mount sizes. There's HE guns for all slots, there are shrapnel guns for all slots. Energy weapons are an overall more varied group, but you still have options for "punching down": nimble targets might evade your plasma cannon but they aren't going to avoid a tachyon lance or high intensity laser.
I was not expecting this much opposition to variety. The existing Large missiles are pretty much all big cumbersome weapons best used against big cumbersome targets, and neither Ballistics nor Energy have this limitation. I guess it's accurate to say "Wait and see" with regards to the future directed energy missiles, the Hydra might actually deliver on what the Hurricane attempts to do.