Provide a histogram similar to the current referring domains, but categorized by the referring domain deciles.

This data isn't 100% accurate because there's no easy way to capture the DR rating of all of the linking domains over time - just as they stand today. It would appear you have that data, but not easily accessible.

These two charts - the first one shows a growing backlink profile ---- the second shows that as its growing, the quality of the profile appears to be declining