Both agree and disagree.
-3.0 - 3.1 Was pretty good i loved Naxx and Ulduar they were lots of fun.
-3.2 Was not so good because you could get full tier 9 for a few badges without doing raids and ToC was pretty horrible.
-3.3 The dungeons were okay to begin with but they became boring after a few weeks. I never tried Icc because my brother told me not to because he thought that the only two fun boss's were Putricide and the Lich king. One day i watched him clear 11/12 bosses in the raid and i had to agree with him.

Although i can't deny that the quests were tons of more fun then classic and tbc quests they were just boring and stupid.
I don't really care much about difficulty as long as the instances are fun and to be honest the 5 man HC were lots of fun in the beginning untill they became one big aoe fest and bosses died under 15 secs.

overall Wrath of the Lich king was an okay expansion. It had some downs but also some improvements which made it a better expansion then tbc if you ask me.