For contrast, all the "coincidences" in the first few episodes of season 1 of Heroes, where these people kept bumping into each other, didn't feel nearly as forced, yet it still required the heavy hand of the writer to make it happen.
Definitely arguable, as I think everything in the entire series of Heroes is forced, but you have a point about BSG being the same way.
And you're right, what is the likelihood that out of all 12 planets, the final five were on the ships to make it out (can't remember which ship Tori was on, if not Galactica).
I have a feeling that all these questions would be explained by the show runners as "divine will." That's where it seemed nearly every resolution in the final hour came from.