Yeah. I think this list has a very (very) rough relationship with how good the cards are, but that isn't really good for much at all.
So I find some additional usefulness in the two components that I don't get from the composite. Knowing what cards are more likely to be gained by the strongest players (modulo the high situation-dependency you note) can be useful for the rest of us, and the hard data are better than our fallible memories. So if Qvist's rankings have two $4 villages in one order and the objective data has them in the opposite order by a decent margin...stuff like that would be revealing.
The other component, which shows how much more mileage strong players get out of specific cards, may also be interesting. This is really even more interesting for the more rarely gained cards (e.g., what are you all doing with Harvest? Maybe I should look.) But a lot of it seems to indicate how much better engine building gets for the Level 40 crowd, which many of us aspire to.
More important, these are overall rankings. On any given board, you can throw them out the window - it doesn't matter that 195 other cards exist which might make card X good or bad. You only have the other 9 which exist right then and there, and that's basically always going to be a lot different than the general case.
I agree in the general case, but there are some splits (Attacks present vs. not; Villages present vs. not, maybe others) where difference in gain rates and success given gain could be instructive.
(I skip the Magic references and shout out to Stef.)
Re: the metric itself. The source of my head-scratching is, you applied a normal CDF to it. People do this all the time, and I'm not sure why - my guess is that it's because they did it all the time in their one stats course.
That baffled me, too, which is why I mentally inserted a call to an empirical CDF function instead of the normal in my comment above. :-) I suppose if we were going to plug this into some analysis that really really cared about normality...but we're not.
So again: I see some value in the two rates separately (gain rate and win|gained), but no strong rationale for normality or for forming a single index. And I would like to see win|not_gained.