One particular thing that I have been wondering about Dorian is when he left his Tevinter lifestyle. Being that he has developed a notable dislike for some of what the place is known for (such as slavery) to leave, I would say he would at least have to be old enough to the point to where he understood it and not wanted to be a part of it though I am getting the feeling that it has only been recently when he abandoned that lifestyle he had there. Any thoughts on this?
I don't think he abandoned Tevinter as soon as he decided he didn't like what was going on. It sounds like something might have happened to finally spur his exile. What that something was, I have no idea, of course, but it's possible I imagine he was trying to help from within/at least rebel against the norm before whatever happened happened.
Either that, or he actually HAS been away from Tevinter for longer and the world going to hell is what made him decide to come forward, help, and make his case known.
I wonder how old Dorian is. I know all our companions are supposed to be 'older', but I get the impression he might be amongst the younger spectrum, though certainly not as young as Alistair was.