I pretty much agree with all your review of DM: very accurate, well done.
About backpedaling, it's quite obviously an attempt to make backward fighting impossible, like you end up doing most of the time in Morrowind and Oblivion, for instance. It's particulary difficult to adapt first when you're using bows. However i didnt make a bow runthrough yet, so i don't know how it works when you get used to no backpedaling. From the two runs i made, i'd say backward move could have been tweaked to be a bit faster.
About your weapon being able to crush enemies in a few strikes, i assume you've played the big sword way. It's even worse when you get rid of Xana and obtain the Dragonsomething weaponswhich make you almost invicible.
Playing it the dagger way kinda deals with this problem, and in my memories, allows you to try different ways to approach melee fighting. Also, besides being basic, i found sneaking phases to remain enjoyable, and plunging daggers in the throat of unaware guards was good fun.
I never used any of the spells, and planned that the next run i'd try would be a staff/spell one, but i'd be interested to know how it feels and if the game makes the magic way entertaining.