A very competent 10 year old, maybe. Watch some of the gameplay trailers to see.
My 13 year old son has completed it already once and is running through it again to get some armor and stuff he missed the first time through. He's also completed Skyrim at least once (maybe twice) by now... and has done more of the side content than I will ever do.
Edit: note that my son eventually did switch HZD to "easy" combat mode, though. Your mileage may vary.