I wouldn't use Dark Souls as any indacator of feeling good. Most of the time I felt plenty frustration and a lot of "Well thats bullshit." It has less emphasis on fun and more on "Show us devs what you can do" And the challenges weren't FUN, they just made me wonder "ok how the hell am I supposed to this along with the other..time killer things going on).
WoW doesn't really need to look at Dark Souls for anything gameplay wise. Maybe in terms of making certain factions of enemies that are scary(Seee the Old Gods and such). Otherwise.. I think Dark Souls needs to stay where it is and not try to be this all can be video game.