Pugging these dungeons as a tank in groups full of people conditioned by Wrath heroics was like placing my genitalia in a garbage disposal, except you can generally only do that once. I ran these dungeons repeatedly. It was not pleasant. By the time I was geared enough to tank the new raids, I was so bitter and hated Cataclysm as an expansion so much that my friends and colleagues (many of whom were lucky enough to have dedicated groups running these dungeons, not being forced to pug as I was) thought I'd gone frothing, barking-mad insane. I tanked in tier 11, but I had no desire to do so; I merely did it out of obligation.
What this meant was that I missed out on getting to enjoy those dungeons. The difficulty of getting groups to avoid Corborus' burrowing, the inevitable fallout of blaming and group disintegration cost me several months when I could have been admiring how well laid-out these dungeons were, looking over their art and enjoying the mechanics on a technical level. There were a lot of cool fights I spent my time gritting my teeth through, a lot of dungeons I endured due to their tuning. It's one of the reasons I like going back and tanking them now.