Perhaps you are all clenching your fists, thinking "Oh Light don't let her get into the tree form shit again!" I promise that this whole post is not about that but Mia from Chronicles of Mia is asking about game changes that she would bring back, can you really expect me to leave out TREE FORM?? But I've already written loads about it and not much more needs to be said. Simply know that it will forever be a gushing wound marring my gamer heart.
Ok, dead horse = beaten, moving on. Speaking of horses, since worgen get some and get to keep their humorous feral cavorting, why not bring back plainsrunning? I never played when that was a thing, but wouldn't it be cool for tauren to just take off on their own two hooves? It would probably make the kodo-haters happy, too.
Next, class quests! Flipping class quests! For spells or mounts or sweet loot. I don't care, I want them back. They distinguish your class from others and create camaraderie among players. Make them involved (note that I didn't say difficult, expensive, or even long) enough and players will look back on them fondly for years. I know WoW is trying to be a game where you aren't required to do much of anything, but come on, class freaking quests! Make the quests easily found, well-explained, and completable solo and I think you can reasonably make them a requirement to obtain...something.
The recent companion pet changes (have they even gone live yet?) where holiday pets lose their summoning reagent, but are limited to their holiday season? That's crap! Don't send my pets away! How about taking away the reagent AND letting me summon them any old time? And while you're at it, I want that Macabre Marionette all year round.