With Guilds cards coming out it seems to be time to check our answers...
Here's my count: (Many are subjective, this is just my take.) These are divided by 10, so victory cards count as 1.2 cards, prizes, knights and rats count weirdly.
Set:
[male lead]/[female lead]/[non-gendered]/[no clear human subject or multiples]
Base:
3/1/6/15.2
[Smithy, woodcutter, militia should be grouped as "male" but don't have a 'lead' character.]
Witch is actually almost neutral... no traditionally female indicators are present. I'm not sure what's on the face there, but it looks lacy so I went with female.
Intrigue:
8.4/0/3/16.4
I'm marking Nobles as 'male' based on clothing, but I don't know enough about clothing to defend this claim. Masquerade I'm leaving as ungendered... there's maybe a hint of stubble to argue otherwise with. Either of those could vary; I feel okay with ruling one apiece. Harem should be female, but again doesn't have a 'lead' according to the rules of the OP.
Seaside:
4/2/5/15.2
Is navigator definitely male? I went with neutral.
Smugglers is all male but with no lead. Bazaar has two male leads.
Alchemy:
3/1/3/5.2
Here, I'm calling scrying pool female, although it could probably go as neutral.
Prosperity:
3/2/0/20
Goons is all-male with no lead.
Cornucopia
1/4.4/2/6.3
I don't know why, but the woman in the foreground of Followers looks to me like the "subject" of the work, as does the man on the right in Horse Traders. Either could've gone in the no-lead category.
Hinterlands
8/2/0/26.6
Weirdly, the name is the only thing that indicates that the Duchess is the subject of the work. The (male?) baby seems to be more emphasized in the image. But the name is Duchess, so I'll mark that as female.
Dark Ages:
16.5/1.5/4/22.2
I'm calling minstrel neutral. Her or his arm is weird, right? I called Armory male.
According to the rules of the original post, my rulings bring this to 13.9 female to 36.9 male, so 27.4% female. My personal vote was 20-25% so not too bad. If we include the cards that have a primary gender (but no clear lead) it comes to 14.9 female to 42.9 male, which would put it at 25.8% female.
I was curious about the interplay between two staggering factors. On the one hand, the assumption of male inclusion as "normal" and female inclusion as "not-normal" makes us notice female presence more, and rate it more highly in our memory. I read a disturbing study about teachers who were asked to approximate what percentage of the discussion in class was occupied by the (half) female students, and teachers overwhelmingly thought the females were dominating conversations even when they were contributing equally. (This might be more about perception of female silence rather than female presence. Still, I was nauseated when I recorded a few classes I taught and gave myself this test.)
On the other hand, this is fighting against the tendency too look at an ungendered image (spy and thief come to mind) and assume it is male, because you know.
The biggest surprise to me was finding that Dark Ages was such a sausage fest. Maybe it's all the Dames, but I remembered it having more women than there were. And yeah, Cornucopia is the only one with more women than men. Like AJD, I thought the presence of women had increased over time, but no, this isn't particularly the case. It's been pretty consistent the whole way with Cornucopia and Dark Ages the only outliers.