Just wanted to comment on this, which I think a lot of people are assuming. I don't think showing up first necessarily means these will be our "most important" characters. I honestly wouldn't be surprised at all if characters like Varric and Vivienne didn't have as deeply embedded plot relevance as some other characters. I think their reveal early might actually be because what was revealed tells us less that would surprise us. Characters with backgrounds that require them to reveal plot elements we don't yet know about may be held until towards the end, even if they're very important to the plot.
Also, your Solas art is amazing. 
Well, they don't have to reveal much about the plot to tell us about a character. I think Vivienne will be important to the plot due to politics, and I think Solas will be important because Fade Expert, it'd be hard for him not to be important.
We already know Varric and Cassandra are likely to be important.
Hopefully due to the time extension and the fact that we have nine set-in-stone companions, they'll be able to make everyone equally important to the plot, and no one will feel like: Why is this person here, exactly? Sort of like, I adore Fenris but he really doesn't influence the plot much unless you allow romancing him to influence you to be anti-mage (or are trying to convince him to be pro-mage).
The initial reveal doesn't mean that they're important, mind you. But they revealed Morrigan and Alistair before, say, Sten, if I remember right. So, "main" companions are likely to be seen first, not only because we'll meet them first but because of their high relevance to the story. If I'm right, it also bumps up Solas's chances at being a romantic interest, since the major plot-related characters are also usually, you know. Romances. Can't imagine why... 