Psst, first law of thermodynamics: Don't talk about thermodynamics ;-)
How many times did the rebels destroy the first death star in your multiverse? If they succeed most of the time, it would take away the tension for me, as they are kind of "meant" to win; If they fail most of the time, there are hundreds of thousands universes left where the empire wins, which would, in my eyes, make the few victories of the rebels pretty much meaningless. (If it's only one time, it would literally make it a "one in a million" shot, like Han said :-D)
At the same time, 1,000,000 is still a very small number to explain how so many universes developed exactly the same except for one event. In my opinion, a big amount of branching points in a relatively short time (~100 years around the OT) doesn't seem very likely.
In the end, it depends if you're writing a dead serious chronicle or if you allow for some fun with "bizarro universes". In the former case, everything has to be thought through and plausible, in the latter case, smaller inconsistencies aren't that much of a problem.