[Discussion] Vet leveling

So I've recently came back to the game with some friends and we've heard mixed opinions on fastest leveling method. Questing? Sewers? wrothgar? Not interested in questing really and seems to be the slowest method anyways. Any care to go into any detail on the fastest ways? If you don't want it to be super public or something, shoot me a message with details if you will. Time is fairly limited so trying to get the most out of my time as I can leveling-speed. Thanks!