sorry about my bad english. im not a native english speaker.
It's not just hack n slash, it's actually extremely well thought out and absolutely demands for you to time your attacks perfectly and use your back-step, thrust attacks, etc etc depending on the situation. It takes a lot of thought rather than just blocking and hitting. It's a great game if you're the kind of person that has the patience to master it. After you get it down, there's nothing more satisfying than killing mob after mob without dying. It's a really hard game, so it's not for everyone. This kind of system could be integrated into skyrim without the huge difficulty though.
Just as a side note, I'd love Dark Souls combat exactly as it is, difficulty and all, in Skyrim. It would definitely not run well with a lot of people though, unfortunately.
Then again there is a balance. Dark Souls is ALL about combat (trust me, you either LOVE it or freaking HATE it), Skyrim is mostly all about story. Most people play Skyrim for the story not necessarily the fighting, so I understand why they wouldn't want this. They're very different games. It's just a personally preferance of mine that makes me say I'd want Skyrims system to be like that.