I agree with @@DT85. The two heroes actually a repeating of Jan and Kyle's adventure. Not 100% yes, but there are lots of similarities, including the voice. But in this instance it can be both a disadvantage and a positive side of the show, as the voice of Hera sounds familiar and undeliberately makes connections with other Star Wars stories.
It is true, that the show is developing around the Ghost crew only, as @ said. But first of all it can actually work out - in the past there've been many shows, which used the same pattern, it was only one point of view. In TCW it was also the case until the last episode of Season 1. Season 2 introduced other sides and characters. Probably this might happen in Rebels, but for now the show can boast with other things, while it could present much more.