Between Cataclysm and Mists of Pandaria, the warlock class saw a near-total redesign that, at this distant remove, we'd have to admit was a runaway success. Class redesigns are always a risky proposition - the dilemma is always between those who find the class reinvigorated and those that liked the class as it was, who now find it unfamiliar and undesirable to play.
The reason I bring this up is because lately, while playing Reaper of Souls, I keep thinking about that warlock redesign and the fact that in RoS Blizzard managed to take a game people generally felt was an unsuccessful sequel and change it in a variety of ways, and in the process so utterly remake people's opinions of it that we get reviews like this in Forbes. This has me thinking about whether or not World of Warcraft is going to see this kind of radical redesign in Warlords of Draenor or not. On the face of it, we're aware of a lot of changes coming - the removal of reforging, stats like hit and expertise, the deflation of stats on gear, health and healing changes - but there's still a lot we don't know about how thorough the redesign of the game is going to be.
Now, to be fair, RoS didn't make any significant mechanical changes - certainly nothing as dramatic as the warlock redesign was. And the warlock redesign came at a time when talents were completely overhauled as well. Clearly, there are various kinds of redesign in any expansion, but how does Warlords of Draenor compare? While we don't have a complete answer, we can compare it to previous expansions.