Yeah, I think this set needed to have an obscure X-Winger as you say, JJ, because it would be less likely to sell as an individual figure due to its obscurity. A character with prominent screen time like Red Leader or Wedge would be much better candidates for single cards. I don't know if Dorovio was in comics or not, but I could see her showing up there instead too, Chewie. It really doesn't bother me at all that she's in this set, especially knowing she's in the background of the film (even if she's not prominent). If she HAD come out on an individual card, I'd be much less certain if I'd buy her though. Here it's like she's bonus!
About the broader view of the Empire and the rebellion... your rationale is perfectly logical, JJ. My own comprehension of the vastness of a galaxy as an adult is nothing like my perception of the films as a kid, where there was just a handful of systems and I thought they were relatively near to each other. Also, there is the budget constraints GL had durting ANH and even later. But using just the films as rationale (which I like to do, even though they're hardly a complete view of what might be logical), GL showed us how things operated in his story. He showed us in ANH that the core of the rebellion were former senators and military men along with young male pilots and soldiers. The audience of the Yavin ceremony appeared to be several hundred men and just Leia. I like to think that the people in that temple represented the vast majority of the rebellion at that time. Then, in ESB we see female console operators in Echo base, and all male Hoth soldiers and pilots. By the time of ROTJ, many alien races had joined in the struggle, and likely a few women operated as pilots (but we do see a few female techs in the meeting room too). As for the Empire, there isn't any evidence that women are a part of it at all, and I think that fits in with Lucas' view that the Empire is a non-just tyrannical regime with no place for women. In the trilogy, women were portrayed either as strong-willed princesses, simple good women like Beru, or they were shady objects of desire like Oola, the Tonnika sisters and so forth. By today's standards that's probably sexist, but it's part of the formula of SW I think. I like to think that in the films we saw the majority of each side's numbers, but I realize that it may be way underestimated by most people's standards. A lot of people think that there were multiple thousands of Star Destroyers in the galaxy, but I feel there were only several dozen! I know logically that wouldn't make sense, in order to patrol/govern a galaxy, but still I like to extrapolate based on what we saw, and I think the Empire would have the majority of its force present at Endor to finally crush their biggest resistance.