I'll be referring to the classes from this sheet, as it's a lot clearer and easier to indicate off:
http://xs113.xs.to/xs113/07132/Groups2.PNGI'll refer to the groups as 1-8 starting at 12 o'clock, and going clockwise.
G1:
The bottom right pair is a perfect example of how it should be done. Immediately recogniseable as male/female and clearly the same class.
The other two designs are a perfect example of what you shouldn't do. The plumage, and shapes of the hats match between genders of different classes, but not with the same class. Basically, switch the girls' hats around. Otherwise, these two classes do a very good job of distinguishing between male/female.
G2:
Far left work fine.
Female on the far right is very easy to confuse with the bottom most class, and you really have to look at her male partner to spot the similarities in costume. Give her the same type of hat as the male, with a ponytail sticking out the back.
Top and Bottom of this group do a reasonable job of differentiating themselves from each other, but you could easily give the top set only the male headwear, and the bottom the female, or vice versa.
My final problem with this group, is that in the top two classes, the females of the pairs are much more heavy set.
G3:
This group is fine in terms of distinguishing the various classes, from one another, but there's very little to no disambiguation between gendre types.
G4:
One of your best groups. A cross somewhere on the female medic's design might not go amiss, but it's not necessary.
G5:
Best group you have. The left most female's hat could be pixelled better, but all the classes, and genders are easily readable.
G6:
One of the most problematic groups. Apart from the right most couple, it's almost impossible to distinguish between sexes, save for from that tiny slither of hair.
The left most, and top most both have near identical costume designs, and to someone unfamiliar with the game, the left most pair could easily be mistaken for male versions of the top most pair. For clarification's sake, give one pair the peak helmet, and the other the flat guard.
G7:
Great group. My only suggestion is to make the bottom left female's cape match her partner's. If you're swapping palettes, she could easily be confused for the class directly above her.
G8:
Top and bottom are fine, left and right are not. A simple fix would be to design the right most female's headwear more like her male counterpart's.
General comments:I've noticed the female's are more readable when their neck area is less cluttered. Consider experimenting with dropping the shoulders a pixel, on the female varients of the heavily armoured classes.
There's A LOT of purple throughout the entire cast, and that isn't helping in distinguishing between classes.
Hope I've helped.