Depends what you mean by 'proper' - getting bogged down in PRINCE 2-type crap would hinder, not enhance, the estimate.
Bottom line is that risk analysis is a means to an end, not the end in itself, and wrapping oneself around the risk axle, to the detriment of more useful activity, perhaps imposes greater risk. As he previous poster states, if the assumptions are incorrect then all the risk analysis in the world isn't going to make a jot of difference.
You are demonstrating exactly the blinkered thinking that we are talking about. I am talking about the high end risk analysis tools used by businesses delivering complex, high value projects. All projects start with assumptions; proper risk assessment tests those assumptions and provides consequence analysis if the assumptions are wrong. Sometimes the risks associated with an assumption change the course of a project.
I am an ACSC graduate and have worked as a staff officer on operations at Div and Bde level. I can categorically that I was never taught or saw anything that resembled effective risk assessment whilst serving. In business, I have been taught and have used class leading risk management tools and techniques and know how powerful they are in both decision making and in the execution of decisions.