...would it be taken as an absolute failure? Just think about it, 1st raiding tier's main raid was a rehashed one from Vanilla, while the other two were small and you almost didn't notice they were there.
3.1 brought just one raid. I can't even imagine how big the outcry would be if 6.2 brought only HFC, without any other content. Yet it was OK back then.
3.2 added a really small raid that was probably the most uninteresting raid ever created (heck, the whole raid happened in one small arena) and an annoying dungeon that was in the same arena + "mounted combat" system (which is terrible, even more terrible than garrison shipyard). The dailies were alright, aside from the vehicle ones, but getting all the things from there was a torment.
3.3 was probably the best WotLK patch, it added a big raid instance and 3 new dungeons, but it was a current tier for 12 months and that was not really nice.
So, my question is, if WotLK came out today, would it be regarded as a "failed expansion"?