I can't say I find the graph particularly interesting. It's suffering from the competitive Dominions community's fundamental brainworm: the sample size is too small to be treated as significant, and this drives a pile of conditional variables to be treated as independent to artificially inflate it. How well nations perform in a given game is dependent on the map they play on, scales/bless/pretender taken, the win conditions, the other nations in the game, the number of other players in the game, the player playing them, the players playing the other nations, random map placement, how much experience each of those players have in general/with that specific nation/against the nations they're facing, any particular metarules in place on the game, the perceptions of comparative national & player strengths & weaknesses, etc. Oh, and let's not forget: what version of the game was played, what mods were used, and what version of those mods. To make things worse still, there are unacknowledged feedback loops at play as well - seasoned players versed in the meta-expectations of the community won't play nations that "aren't competitive" or that "are noob traps", which means over time the people that play "bad" nations will tend to be less experienced and thus lose more, reinforcing the notion that they're bad, etc. And to pile on to that, once we introduce mods, we have mod design being fed & reinforced by community perceptions. [Edit: it probably doesn't need said, but these perceptions also feed & reinforce map design & selection in a similar manner.]
All of that isn't to say that some nations aren't just plain better than others, it's to say that a graph like this isn't interesting b/c of how much data it omits in the interest of reaching an easily-quantifiable unequivocal universal conclusion. Which, again, is a problem that's been recurring in the competitive Dominions community for as long as it's existed: they want to treat this as if it's as easy to compare nations in this game as in games with far more streamlined variables - and even more so, ones with more data points. Quantity smudges out a lot of the above problems, but a sample size this small (and stripped of all data but nation + wins) makes this uninformative - again, not least b/c it does not even tell us if we're comparing the same nations since mods profoundly change how the game is played and how strong or weak given nations are. And that's the problem with collecting data for something like this - there aren't enough games available for us to compare only games where even just the mods used is stable. So we end up with what we have here: disparate data points being treated as interchangeable in order to drive up the sample size to a number that doesn't look completely arbitrary.
tl;dr: you can make an analysis like this, and it can be interesting, but not w/o a lot more information about the source data set.