make sure you are not confusing harshness with bounce as they do tend to be bloody hard, YOU WILL FEEL EVERY SMALL IMPERFECTION IN ROAD.
The dampers normal thing is to leak after a time especially if people have not used the adjusters for a long time then do as the seals dry out this is what happened to mine.
you can always speak to NIGEL, CHASSIS DYNAMICS on 01604 708101.
CHASSIS DYNAMICS & AVO are one and the same.
The front adjuster adjust rebound only whereas the rears adjust the bump and rebound.
The front spring rate is 300lb"(9") and the rear 200lb"(12") on a 2WD SIERRA COSWORTH, just to give you an idea the std front sierra cos is 190lb" from ford, so you can see these were never going to be a comfy set up.
A lot of people set them way to low and this compresses the spring adding PRE LOAD which stiffens the rate further, instead of using a shorter spring, I have mine set at std ride height -1" that's all.
It might be a good bet to speak to NIGEL as he is a very knowledgeable man, and happy to talk cars all day.
tabetha