You will find that the biggest weakness in most people's descending skills on the road is related to lack of bike handling skills. I have seen so many people fall off descending on the road when they come across the most minor obstacle, when a simple change in tactic might have avoided it.
If you want to improve your descending skills onroad I would recommend spending some time mountain biking offroad. Mountain biking allows you to improve the way in which you control and manuevre your bike far greater than you ever would purely riding onroad. It also helps to build up confidence.
The descending skills on both bikes are very similar (apart from different hand positions on brakes), but mountain biking requires you to shift your weight around that little bit more to avoid obstacles. The more you practice offroad the faster you get. Then when it comes to descending onroad it is easy as there are generally no obstacles to avoid, and if they were you would be a lot more comfortable making the right decision.
