Definitely tongue-in-cheek!
It seemed definitely tongue-in-cheek to me! I don't think it was making fun of this genre as such, but playing with Norse mythology using it.
I thought it was really good (I had read it had 'very mild scares' prior to watching so I wasn't expecting a horror), & even though I'm British & don't know all of the fairy tales & fables referred to in it, I really liked the sense of humour & found it very similar to my own. It felt a little offbeat & when I read that 3 or 4 or the actors are comedians in Norway it made sense as they dead-panned so well!
I was impressed with the effects actually (I think I had expected it to be more like the recent US 'creature-features' like Sharknado etc.), & I also really fell in love with the stunning scenery - I can see how the myths must have been born there.