I agree with you. If the show had found a way to introduce Dedra and Mon Mothma in the pilot, it would catch people more easily. It's odd for a show to wait until the 4th episode to introduce the two best main characters.

In fact, I'll go one step further and say that Mon Mothma should have been a co-lead of the series with her name and face equal to Cassian in the marketing. That would have better communicated to people what kind of show it is.