Well I'm not familiar with every little detail ofthe setting-though I do probably know more than the average player-but I don't think people in Thedas have the means to enact artificial insemination. Maybe that's a thing that's been available in crude manner for longer than I realized in our real world, so they could potentially have something like it in Thedas, but it's never come up as something which could be done.
As far as the marriage issue, my understanding is that marriage in name only could have worked if Dorian had been willing to just "lie back and think of Tevinter" until a baby was made, but Dorian specifically did not want to compromise his identity for the sake of his family lineage. An irrational choice? Definitely. But not an unbelievable one in my view at least.
