-Warfronts- I liked the idea of warfronts because it blends elements of Warcraft III with World of Warcraft, however, it's not a PvP battleground or instance, it's PvE so given time, it's a guaranteed win so many people are starting to AFK in the warfront. Beyond that, there is only one warfront to participate in right now. Also, when preparing for a warfront, Blizzard presents you with daily quests to help "aid" the warfront, however, your daily quest turn ins have no bases on the progression of warfront. The warfront will continue to advance at the same rate no matter if you do zero quests or everyone does all the quests.
Class abilities were reworked dramatically across the board, with some still needing a serious balance pass. That left many players not only feeling underpowered, but having to learn how to play their characters all over again. Bosses in large-group raid dungeons that were easily killed each week by experienced guilds of players suddenly became challenging again, or worse, completely unkillable, halting forward momentum on old content for a good chunk of the high-end player base.