That tabula rasa is what makes it good.
And I disagree that the inflection or delivery of the lines requires a specific interpretation (which is basically what you're saying with your tabula rasa complaint, so I don't really understand your point).
Any personality the PC develops needs to come from the player, not the writers. The player only really gets to roleplay if he has some sense of authorship.
An interactive story where I get little or no input, like Mass Effect, doesn't interest me at all.
I disagree with pretty much everything you wrote in this thread. 
If I can make up whatever I want about my character and it is never mentioned in the game or has any consequences, then it is pointless. The Inquisitor isn't a fleshed out character like the Warden or Hawke, s/he is your avatar in the game.
What I would like to see is my character changing according to the choices I make in the game and the environment reflecting those choices. Remember alignment from AD&D? BG1+2? Being rude, evil and greedy meant some people wouldn't even speak to you. Being good meant people were more willing to talk to you.
I -could- create the personality, backstory and interests of my Inquisitor for myself. To some degree we've always done that with our DA characters, for example when it comes to their romances. But am I supposed to remember all that next year? Dragon Age Keep thoroughly confused me at first because I have ~16 characters to choose from and I mostly went with the standard appearances (cause single player game). I didn't remember much about the individual playthroughs. Who was my love interest as human noble? When I played a gay dwarf, who was the father of Morrigan's kid? As female mage Hawke, did Carver die, become a Warden or become a Templar?
If I can't even remember those details, how am I supposed to remember -everything- about my characters? I might want to play 3-4 more, just to see the differences.
I expect that my character has some sort of impact, that he's part of a living, breathing world. But if the world of Thedas doesn't give me any feedback, then why am I even bothering?
It's not just the origins, it's all of the game. It doesn't matter if you saved the refugees in the Hinterlands or if you spoke out for the mages, the next conversation about it starts at zero. Tabula Rasa.
It doesn't matter if you play as a faithful follower of Andraste or oppose the chantry and its teachings. Even when you get the chance to speak about it, it never changes anything. Same for every other issue. It doesn't matter if you are brilliant or stupid. Rude or polite. Helpful or merciless. The world doesn't care, so why should I?
And really, I am actually supposed to come up with my own story despite playing a story driven RPG that limits and railroads me? Could you please make up your mind, BioWare?
I expect DA:I to remember that I use sarcasm a lot. I expect it to remember that I'm honest. I expect it to remember at least the core attributes of my character and adjust new conversations, offer quests and have people react to my presence accordingly.
Oh, and don't tell me that isn't possible because BioWare already did that in previous games.