I personally found Denova challenging but not unduly so, I'm glad to see this level of challenge in a normal mode.
I wouldn't be against an easier "raid finder" type mode but I'm glad the challenge level for the 1.2 raid at its starting difficulty is as high as it is.
One of WoWs great mistakes was making all of its previous content irrelevant after each new patch, if the difficulty is this hard and you need gear from previous ops to even attempt it then people will continue running the older ops which creates a vibrant end game community. Much preferable in my opinion to a few million people constantly running the same raid tier each week with a few dozen other raids sitting empty.....
My progression group doesn't step into the old raids as much anymore, except when we're taking an alt or a few new members through to help them experience a taste of end-game and get prepped for running their own groups, but I think they gave a great incentive by providing Black Hole commendations from Nightmare KP. It gives us a reason to revisit it, especially in terms of the earpiece/implant upgrades.
That and I still don't have that mount