These graphs are super interesting. I noticed browsing the profiles of a lot of the top players that there seems to be a general trend of somewhat stagnant level and then a quick jump of 5 or so levels in a short time period followed by another long stagnant period.
I wonder if this is due to something just clicking, elevating the overall play level. I think it seems to suggest that, but really, I'm not sure I can remember specific things at these critical points which boosted my game. I mostly just remember getting really hot and riding it out.
Looking at my graph, there appear to be two big jumps, one around late April and the other one in mid-September. When I saw the first one, I realized immediately "hey, that's probably right about when Cornucopia was released!" And, yep, Cornucopia was responsible for, like, seven or eight levels of improvement. Not sure why the second jump happened, though; that was before Hinterlands (which did not have anywhere near the same effect.)
Been dropping a little bit recently, which makes sense: the competition on Iso seems a lot stiffer than it's ever been.