It's not about pleasing "some" people its the fact that different people want different things, the same person is not complaining about the dungeons being too hard in cata and too easy in MoP, its the people who are happy with cata style dungeons (4.0) don't post nearly as much as the people who hated them and now in MoP the people who hate that they are too easy will rage and the people that like their accessibility won't comment nearly as much on the forums. Don't assume its the same people complaining that dungeons are both too easy in some cases and too hard in others
Also on the note of this, when I was back on aman'thul, possibly one of the worst oceanic realms (2nd or 3rd worst) had 3 people on the volcanic drakes 3 days into the expansion so it's really not a comparison of how hard the content is when 4.0 were considered really hard and they got their's in a very similar time frame whilst also juggling raiding commitments - no raids = bored wow players = other content is done a lot faster