I hope you are right. Ie --- I hope we get to dive a little deeper into the custom character's history (or define it more explicitly through dialogue...or...something). I guess I feel like with the Origin chars as an option...well, it makes me think that there is no awesome secret waiting for me about my custom char specifically. Ie, that playing a custom char is somehow the wrong choice if one wants the deepest most satisfying play through. But I could be totally wrong.
And as you say...it is just the EA after all --- although --- it might be more like playing through Ostagar AND the Elven camp in DAO. Isn't the EA like the first 1/4 of the game, given its size on the map? Again, I could be wrong about that too.
I also know I am likely supposed to be approaching this as a party thing anyway, rather than as a single player with companions. But it is hard to break the habit of every rpg ever! lol
What we're likely to find is that the main story will be our character development. The Origin characters have established backstories precisely because they can be companions, even if one were to choose one of the other Origin characters to play as. Speaking very generally here, but all of the comps in both DA and ME had established backstories too. The only difference being that we couldn't choose one of them to play as. We don't even have to limit ourselves to just DA or ME. All of the side characters in the Witcher series have established histories. We can roll back to BG 1 and 2 and find the same thing. This is about a third of the game, and I'm not even sure that everything that will be live in a full release is available now. It could be, but as of now, I have no way to know.