I think you overestimate their chances!
…because in my experience, Rebels simply don't win. I'm at nine games now, and Imperials have won every match. I've heard of other people winning with Rebels, and even played at a table next to a game where it happened, but I haven't seen it personally.
What happens instead is that the Rebels lose their first ship no later than the second round of engagement. Usually it's either Biggs or, if Biggs isn't present, Wedge; that leaves the Rebel side tied or slightly behind on points even if they've managed to bag a pair of TIEs--which, given that TIEs usually have either focus or an evade token, is unlikely.
Now the Rebels are looking at a game where they're behind on points with one of their key pilots off the board. They're also still outnumbered somewhere between 2:1 and 3:1, depending on list choices. The Imperial player has the tactical initiative: depending on board position, he or she can either play aggressively if another kill looks likely, or play conservatively and just run out the clock.
So, to reiterate, it looks like one TIE per round is an acceptable Imperial loss rate, and you have to exceed that for Rebels to pull ahead. And I just can't see how that happens, barring a very lucky streak for the Rebels. So what am I doing wrong, and/or what's wrong with my logic here? Those of you who play Rebels and win consistently, what are your lists, and what are your tactics?