single backlog requirements & incidents

I have also fought with this issue, and have had to work around the tools limitations. My general approach is to make sure everything is a requirement, as that appears to be the sole view that can give me insight as needed; Planning -> Requirements. With regards to defects, the only way is to generate a requirement form the incident and then we preface those with DEFECT: so that we can identify them in the aforementioned view. As you noted, changes to the requirement are not captured in the incident but there is an association created when you create the requirement form the defect. I have hard that the next release is supposed to mitigate some of these non-Agile approaches that have been forced in to the workflow of the tool.