Call me thick, but I only now understood the visualisation below the line chart - it is a monthly horizontal normalized stacked bar, right?
In its current form it shows the ratio of relative strength in the win and loose categories. I personally have a hard time making anything of it since my stats of playing stronger/weaker opponents is skewed.
I would suggest a very simple change: switch the relative strength and results dimension in the visualisation. It will very easily show you the trend in your win ratio for stronger and weaker opponents, which is a sign of evolution if they are not equal.
Personally, I often resort to do it by hand but having it monthly is a drag.
Anyway, it is a suggestion on a feature which is already lightyears ahead of other servers so - thanks for the nice website!!!