They actually sound a little light but the spring rate varies with spring location and geometry. Is it a harsh metal to metal hit? If it is you are likely bottoming out the shock. Try putting the compression damping at max and see how it feels over the same pothole. Limit your experimentation to a single pothole for comparison purposes.
One thing folks often donít understand is that lowering the car generally requires higher spring rates to prevent bottoming out the suspension. The lower you go the stiffer it needs to be in general. Of course there are exceptions but this is the general rule. It is also why folks often complain of a harsh ride, especially if the coilover shocks have significantly less travel than the stock shock. This is why I often try to steer folks away from conversion coilovers....
I agree, if you take a stock camaro with four inches of compression travel and lower it two inches, then you only have two inches of compression travel remaining. It's going to take a much stiffer coil to reduce wheel movement upwards when you hit a bump. But two inches of bump travel won't be able to absorb a bump like four inches does.
Stock Camaro coils are very soft and when the car hits a large bump or pot hole, the suspension hits the bump stops. When you lower the car it hits the bump stops sooner and it may be nearly hitting them now.
I would be looking at shock travel, and any bump stops that are on the shock shaft, then look at factory bump stops. I'd like to see 3/4" or 1" to the factory bump stop, the shock shaft bump stop will probably be closer, more like 1/2" but I prefer using the factory bump stop to limit travel. It takes the load off the shock. Trim your factory bump stop if it doesn't have 3/4" gap, try to keep the pointed shape, not flat, so the rate is progressive. I have found the factory Camaro seats make the ride worse because the seat springs cause the driver to bounce a lot. Tires make a difference in ride too, also air pressure settings. Oversize tires don't need 35 psi, try 28 for street driving. lower pressures reduce the spring rate of your tires. The air volume inside the tire casing affects the pressure you need to carry a load. The larger the tire, the less pressure needed, but a First Gen Camaro with stock poor front geometry will need some extra pressure to prevent tire edge roll over since the tire won't have ideal camber. If you have improved the geometry with tall ball joints and more caster, then less pressure works well.
450 is a good rate for a street car if the shocks are set right. For performance use you need a 600 to 650 coil to properly support the car and prevent hitting the bump stops all the time. Performance springs are needed when you have wide wheels and tires and lots of grip. If you are running 7" wide rims with BFG Radial TA's, then you don't need as much spring rate. With higher rate springs, the shock "bump" (compression) setting should be lowered because the spring is doing more work of supporting the car, or the wheel mass upward travel when a bump is hit. If you have soft rate coils, the compression setting needs to be raised to make up for the lack of spring rate. When you have too much compression in a shock it screws up the handling feel pretty quickly.