I'd agree with Karlsson and Subban, but Doughty is as elite as they come defensively. He's up there with Vlasic and Hjalmarsson as the best defensive defenseman in the league. I have Larsson just below their level (and he has every chance of being on their level in time).
I agree about Doughty, I was rambling too much there, he is very allround in his play.
The most offensive dmen are usually able to play good defense too but they are depending on their teammates supporting them during their offensive rushes where they suddenly start acting like forwards. They are acting like players with two roles/positions, Karlsson is a good example.