5. Warlords of Draenor
I think for the most part this is where everyone will have this expansion. It is not that it was bad it was the fact that the expansion as a whole lacked depth. Also the Garrison while seemed like a great idea at the time really didn't turn out what everyone wanted it to be. Now as for positives the initial questing leveling experience was probably the best they have ever done.
4. The Burning Crusade
Now this ranking might surprise people. Now if WoD was the best leveling up experience Burning Crusade was definitely the worst. Everything was so far from everything else and Blizzard had not yet realized that splitting up the factions would be a good thing. We also had heroics entry based upon reputation which really was a poor way of gating them to the ilvl system that is in place today. Raiding was great if you were in a good guild if you weren't then you were then useless and ran Karazhan exclusively.
An expansion that gets a lot of flack because of the 1-60 revamp that was a major part of the expansion that not a lot of people ever did. The lore of the expansion built on the good that Wrath had started. At launch the heroics were too difficult to what Wrath players were used to, but that was later fixed. Raiding started on the same curve and because of it we saw the LFR added to the game, along with major pillars of Void Storage and Transmog something we wouldn't be able to do without.
2. Mists of Pandaria
1. Wrath of the Lich King
The expansion which brought many of the features that have made the game as popular as it was. It was also the expansion that made things easier for the everyday player while still giving a challenge to the more experienced player something that was asked for since the extreme difficulty of BC. It really isn't a doubt that this besides being the best received expansion was the most popular time of the game itself.
There you have it my ranking of WoW expansions. What is your ranking? As always let me know what you think in one way or another.