I have been chasing D term noise on my copter for a little while now, which is weird because it used to be flying great. In this video I show how I tracked the issue down to several mechanical issues. The takeaway from this video is that if your copter was tuned great yesterday and then your traces start looking terrible, it's probably that something mechanical has changed. Chasing the mechanical issue around with the tune is not the right approach... fix the mechanical issue!
This is a great example of how a focus on and awareness of tuning helps you track down mechanical issues with your copter. At high throttle, my copter started acting like it had excess D gain even though I hadn't changed the tune at all. This is indicative of an increase in gyro noise. It took me a little while to finally accept that conclusion, but if I wasn't paying close attention to the tune, I might have missed the issue entirely.