I like the way of D:OS1 character creating. Two with my Ideas and two with there own story [...]
I liked that as well, and would be glad if the possibility would be there again.
As for the overall discussion, my take on the companion topic is that we'll get to chose all of them in the prison (as all 4 are supposed to be Sourcerers). I'm not sure if I'm interpreting the available information correctly, though. At least I hope not.
For one, this would mean that whomever we pick at the beginning, we're stuck with them for the remainder of the game. In D:OS (and most other party based RPGs), I can swap out companions if the need arises or I get fed up with some of them. D:OS was already quite low on companion choices, and I ended up with only one and a hireling, but at least I had that choice.
If, in D:OS2, all available companions are those 3 that escape prison with me, I'd be pretty disappointed.
As for the concerns about the companion backstories, that is something I don't see as critical. To me, companion origins and elaborate backstories should go well together and I'd expect D:OS2 companions to be much richer and exciting than any of the D:OS crowd. I also would hope for longer and more involved companion quests. Honestly, I fail to see how a origin/race/class/gender combination would prevent writers to come up with complementing personality, backstory and character arc for that companion. I can't imagine that all this is left to the tag system alone with no specific writing tailored to each possible companion.
Sure, the available companions may be dictated by race and gender (which would already give us more choice than the meager 4 from D:OS), and instead of chosing the Mage from the Inn or the Archer from the Cage we'd have the Mage from Cell 1 (who happens to be a female Elf) or the Archer from Cell 4 (male Dwarf). Doesn't mean they have to be bland or more generic than Jahan or Bairdotr. In fact, I'd think with the number of writers working on D:OS2 they should be way more interesting instead.