The main problem regarding gender balance in nuTrek is that they took the characters of a show from the 60s and transported it into the 21st century. That's why you have the black girl in miniskirts still acting basically as the receptionist (and love interest), but nothing more substantial.
Then there's the sexism coming from the writers, because they think the story and script are elevated by threesomes and women dressing down for no reason during a dialogue.
Deep Space Nine had better gender and ethnic balance.
Voyager had better gender and ethnic balance. Heck, Captain and chief engineer were finally women. Only in season 4 they lost the ball when they introduced Sex Object of Nine in skintight catsuits to boobs the ratings, err, boost the ratings.
Let's not talk about Enterprise, because that was silly. Hoshi, the receptionist again, and T'Boob. And then the mirror universe episode where they suddenly run around with bear bellies to sex it up.
I think I agree that DS9 had the best approach to gender but even in DS9 there were twice as many recurring male characters as women.
Voyager suffered a bit too much from the Smurfette principle. Its high profile women were in more senior positions than ever before but none of Janeway's senior staff were women until Chakotay put Torres forward and they didn't give the women below them a whole lot to do. Seska was a great villain though - it's a shame they felt the need to sexualise elements of her character.
The catsuits and mini skirts are so iconic I can't bring myself to hate them but more power to Aisha Hinds as Darwin - she certainly has some meat on her bones. I would have preferred them to re-use Ilia, personally, but I hope they feature Darwin again, and in the comics as well.