The only issues charts you’re going to find are in the project’s Measures page, where you’ll find bubble charts that show the files in the project, not individual issues.
Why isn’t the chart you’re looking for available? Well first, everyone’s going to have their own ideas of “Top 10 issues”. Second, we feel it’s far more important to focus not so much on remediation, but on keeping new code clean, so that’s what the interface helps you focus on. Okay yes, if after the first analysis you find you blocker bugs in old code, you do probably want to go ahead and fix them. But after the initial settling in period, you really do want to focus on the New Code Period.
Also, I need to make sure you understand that the list of rules you’re seeing on the Issues page isn’t a “top 15” by any measure but volume. By default, that list is the 15 rules (this is expandable to 100) with the most open issues. There’s really no other significance to that list, so you probably shouldn’t use it for prioritization until after you’ve filtered your issue set by maybe type and severity.