Well, let's run down the list....
Unlikely hero, humble beginnings,
I'm not at all sure humble beginnings applies to DA. Two of the DA starts are outright nobles, and magi don't really count either, do they?
As for unlikely, it depends on what you consider a
likely hero. Although to some extent this is captured by the Grey Wardens' less-than-beloved condition at the beginning. I don't see anything particularly unlikely about the ME1 hero.
Another question is whether the game can subvert the whole concept of the hero in the first place.
The Longest Journey (not an RPG) did this to some extent.
Planescape:Torment too. But it's difficult because there's no way to avoid the player's primary role in shaping the game-world. Personally, I'd love a CRPG equivalent of
en.wikipedia.org/wiki/Rosencrantz_and_Guildenstern_Are_Dead, but I think it would bomb in the marketplace.
(First time I tried the new link functionality on these boards. Let's see how that worked.)
Note that Bioware's KotOR is an exception to this formula in certain crucial respects.
the great evil bad guy is exposed early and does something to impact the hero. Hero must gather allies / an army and defeat evil bad guy.
Well, it's difficult to avoid having an ultimate bad guy. Some of the Ultimas did; PS:T again, in a sense, and some early RPGs like M&M 1. If you don't have someone or something to defeat, it's hard to give the game a satisfying ending.
Exposing the ultimate bad guy early isn't always the case in Bioware games. NWN1, SoU, and HotU: nope, all 3. ME1, not exactly.
As for having this bad guy affect the PC, that gives focus to the whole affair. Take Morrowind; that bad guy didn't see very threatening, because he
isn't threatening, except in a very, very long-term sense.
Personally, I don't know how many more stories I can play with that "hero's journey" archetype.
Your alternative?