Asgardians were always aliens. Even in comics they more or less do combine science and mysticism.
These are obviously magical beings who live in an obviously magical realm who also have access to advanced technology. That more or less describes the comic book versions too.
I had no problem with the humor in TDW. You can do a fantasy movie with some humor in it. Humor doesn't take away from the fantasy aspects. With all that said..a movie like Ragnarok should be the darkest of the Thor films since it deals with their version of the Apocalypse. Though I wouldn't mind some light humor in the very beginning of the movie before things get serious.
Also the problem is one of the most popular characters is Loki and his personality type is pretty much one of those people with a dry wit and most of the humor comes from him.