Yes I think so, the average quality of player has vastly improved. I played in a top 40 guild in Sunwell but I'd probably struggle now as would a lot of the people I played with, the standard when I stopped playing was far higher and some of the encounters far more complex.
That said my enthusiasm was not what it had been during Sunwell so that contributed, I knew my class and role inside out and knew encounters inside out before facing them too, in Cata/MoP I could not be bothered with any of that any more, perhaps that had more bearing on my performance rather than the increasing difficulty.
There was also more open discussions on bosses before they were downed back then too, EJ had threads on M'uru etc before anyone had killed it and certainly whilst the 'chasing pack' were still trying to kill it.
We already had to use things like Drums of Battle to give us the edge when in Sunwell the first time so maybe the place was just too damn tightly tuned.