The main issue with Cataclysm, in my opinion, is the fact that there's SIGNIFICANTLY more grinding to do in order to get anything done (compared to Wrath of the Lich King).

Considering I entered the game late-BC and only got to raid in Wrath, the amount of required grinding was... just right. Most of the reputation grinds were done rather quickly, save for Hodir, which didn't take much to finish. Once the main quest line was done, we resorted to turning in the Ulduar scrap thingies and doing their dailies, but it still flowed rather well.

We look at Cataclsym, and while I enjoy the content very much, I've noticed a few... errors... in their approach to designing this expansion:
GRINDING. We enter Tol'Barad, and.... Oh hey. Bunch of blue exclamation marks, filled with boring, "go here, kill this, fetch that" type of quests, forcing players to repetitively do these time-consuming yet boring dailies from neutral to exalted. Worse, the exalted trinket, "Mirror of Broken Images", was required by most guilds because of its high mitigation through resistance. Other trinkets were... Sub-par.
TOO LINEAR. With Wrath, playing 2 characters, one could reach from 70 to 80 without crossing over ANY quests, and it felt like playing another side of the storyline. Do I want to go from Borean, then to Dragonblight, then to Scholazar and finish up in Icecrown? Or do I want to go to Howling Fjord, Grizzly Hills, Zul'Drak, then ding in Storm Peaks? Not to mention, the instance choices were fantastic; although it got grindy and old after... HUNDREDS of runs for Emblems of Frost and such, the burnout didn't happen until the JP conversion. (at least for me) "We look at Cata, and... Oh hey, I can go to Hyjal or Vashj'ir! And then... Oh, Deepholm... I'm already 84? Oh... Gotta go to Twilight Highlands. Uldum? Why would I... Ohh, I leveled too much in Vashj'ir... I alrady out-leveled it..." And then the grind begins. On nearly ALL factions.

Not to mention... Most of the quests in Wrath had little hubs that we could go to once we got bored of the main questline, and skip most of the irrelevant finishers. Whereas with Cata, well, if you stray from the main quest, you're stuck with dungeons or good'ol' grindin'.

As much as I love Cata and raiding, I'm tired of grinding. Now, excuse me, as I help the guild get the legendary staff and work on exalted with Avengers of Hyjal... 21k rep purely from bosses sound like total bliss.