Well, my voice sounds similar irl and I can assure you that I can sound aggressive at times and still come off as a confident and educated business woman...it's my job. 
The VA does a great job doing the same. I'll have to go back and record the ball scene for you guys where she has to be all political.
So a British accent is educated, and American is not? Um, are you sure you want to go there?
Oh, my... Lemme just take my foot out of my mouth, cause I think I managed to shove it all the way down my throat...
I loved Jennifer Hale's voicing of Shepard, and that was an American accent. And her pitch is slightly lower. Her voice was awesome for an intimidating character, but she was also great at delivering diplomatic lines.
But I cannot enjoy the American VA in DA:I the same way. I cannot quite put my finger on the reason why. Is it because the accent sounds just a bit out of place for me in a fantasy setting? Is it because the delivery is a bit wooden at times? Or is it simply because I want to have Hale voicing the character?
Anyway, I've spoken out of turn, and I apologize if I've offended 