Dragon Soul - the whole twilight cult thing seemed a bit silly as they were never a problem previously in the game, it's like if they made the next big baddies in the next expansion the Venture company or something. Beyond that, never felt like you were actually fighting Death Wing, and the re-used boss models and atmosphere seemed really lame for being the end of what could've been a really cool story. Felt like they tried too hard to bring in other elements, like the infinite dragon flight and well of eternity and kinda killed them off, when they could've been awesome raids at some point in the future in their own right.
I actually didn't mind Trial of the Crusader - sure there was no trash, but I don't think that would qualify as being a horrible raid. I got the feeling blizz wanted to try an experiment here. The bosses were fun, the twin valks with the black and white theme and Anub'arak were very cool, and the faction of champs fight was very interesting as well. Personally I thought it was a cool, but very short raid, I think the brought it out as a way to get people into ICC very easily. If they hadn't done that, ICC might not have been as popular as it is.