Twitch numbers may not be a solid metric to determine quality, but using forums like MMO-Champion to do so is even worse. The Twitch numbers at least show that Blizzard is doing something right to getting people involved in the game, since the buzz is more noticeable now than at the start of Legion. The complaints that I have seen here do not reflect the thoughts I have seen while in-game like in my guild, or on other social channels. That's not to say there are no problems, but they are way overblown on these forums and extremely hyperbolic. If this forum is representing the current state of the game, then this expansion is the worst thing ever created by man, just like every other expansion that has been released in the past.
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I wouldn't mind a nearly complete retcon of The Burning Crusade as well (I don't mind the Draenei retcon in retrospect as much as back then though). By far the worst expansion from a story perspective. People say that WoD made no sense, but TBC butchered nearly every character from WarCraft 3, especially Kael'thas. So glad they retconned Illidan in Legion, but I will never get over what Blizzard did to Kael'thas.