Well all of them weren't a proper raid except for maybe BoT or Firelands. A raid should be lots of trash between bosses, not a small pack between them.
BWD was to small, though it did have an epic setting with Nefarian and he's experiments.
Firelands, for me, was bad because the whole idea of open zone and bosses is really dumb.
Dragonsoul is us chasing deathwing and he's tentacles.
To4w was just to small, but fun fights.
The only raid I haven't mention and for which I voted for is BoT. Only reason is it felt like a raid.
I don't wanna talk about the boss mechanics, most of them were very complex except for whole DS and Baleroc.
^comes from a person who done everything on normal mode.