The development of DA:O was probably mostly done on back-burner in the early years. It was a Bioware-IP without publisher. In the beginning, many steps had to be taken to develop the world, and in the end, a year was spent tweaking the game to also be possible play on and port to the consoles.
So the development time of DA:O isn't directly comparable to anything else. What can be said about it, is that it was enough. And that, I suppose, is the important part.
In the case of DA2, I think the developers did a brilliant work of fitting in the game into the schedules. Really well done, even if I didn't like the game, as it was. And they could have saved work if they had reused more resources from DA:O, rather than restyle so much.
And in that, lies the main mistake of DA2: They figured players wanted something different. I cannot help myself from thinking that EA transfers, 'game-design-consultants', marketing dudes, EA-influence in short, had a lot to do with that. Because the changes sort of went into the direction of EA's stereotyphical and failed view of what a gamer is.
(I think Bioware's view might actually be worse

, at least after these years of BSN-turmoil, but I think they're closer to reality

, and thus, maybe, also less insulting, even if they're uglier

).
I see the re-styling of DA in DA2 as the biggest problem for that game, not the development time. But of course, on that development time, DA2 could never have done DA full justice. But it could have been a good game, a sort of brief installment in the DA franchise. But then it shouldn't have been named "2". But whatever, no, development time was probably not enough in any case.
But all that is now water under the bridge.
And DA:I will be an absolutely fantastic game. Better than DA:O, better than Skyrim. Maybe even better than BG. At least for anyone caring to experience it, itself, rather than griping about differences to DA2 or DA:O.
The DA future is bright.