Can't rate a game down if your machine isn't up to the task.
Not sure what you mean with 'bad difficulty settings' - it's super easy to change the difficulty. Care to elaborate?
It sounds like he is playing on a console. I had a lot of frame rate issues on my PS3. I think its perfectly fair because it is on the developers shoulders to make sure the game is optimized for consoles. I have not played much of the game but difficulty wise it feels super unbalanced. The game encourages you to explore but if you take one wrong step your fighting crap 80X more powerful than you. You also cannot skip the side missions as you do not level up properly if you do. Not to bash the game it was just my experience. Imo side missions should be optional not mandatory. I had similar problems with borderlands 2 as you could not progress through the end of the game unless you did a crap load of side quests, most of them being annoying fetch quests. I had to pretty much use some cheap glitch to beat the last boss .
Sounds NOTHING like skyrim on PC. Side quests are optional - total free roaming and ability to change the difficulty at any point in the game. But yeah, even on PC the GFX weren't anywhere near as well optimised as Fallout 3 or New Vegas.
Borderlands is the same though on PC - if you don't complete every quest you get punished very quickly.