ICC is, to an extent, a bunch of random bosses, I can't argue that. But they are thematically emblematic of the whole expansion. As a character fighting through that, you're finishing the last remnants of the Cult of the Damned, jetpacking through the air fighting the Horde / Alliance, fighting the ultimate representations of plague and cold, destroying the final remaining undead nerubians, and removing the Lich King's ability to raise more undead.

Marrowgar, Rotface and Festergut are all fairly generic, and all could have stood to be trimmed (though Marrowgar still works well as an intro). But with all the others, even if most were invented for ICC, I still get what they're meant to be.

My character, having survived rivers of liquid plague, cold so unbearable it can kill you with seconds of exposure, and personally come face to face with the Lich King and killed him, feels like she's overcome the impossible.

In Dragon Soul, she's stood on a dragon who's proven to be comically bad at his job and spent an hour and a half killing tentacles. All I imagine she's thinking by the end of that is "my arms hurt, and I am so goddamn sick of fighting tentacles."