I'm 50 hours into Asgard's Wrath now, and it looks like I still have a long way to go.
That's 50 hours of legitimate content, not backtracking and grinding. When coming back to a place to unlock side areas and dungeons the quick travel and level design keep your backtracking to a minimum. Even in AAA flat games of this length the play times are inflated by uninspired tedious fluff to get a shiny number to market. This game is for real, in all the side content is crafted with the same quality as the main quest, lacking only in story from the main route. 
I have died a few times but not enough to be frustrated. Not DS level of hard but harder than most games.
I don't find the game-play repetitive because the game has very good pacing of the combat and puzzles mixed in. The combat in itself quickly expands as you start piling on weapons, abilities, and animal followers.