You should understand, that Blizzard
EXPERIMENTED with flying combat and quests in the past - between WotLK and Cata. If such experiments aren't successful, they usually add them as fun quests. The result of this experiments -
this quest. As you can see, they failed. But it doesn't mean, that content, designed for flying, isn't possible. For example I have several ideas about flying content. "Sky diving" race quest for example, where you have to reach finish as fast, as possible, while balancing between dive speed and amount of control, required to avoid obstacles. But of course it needs realistic flying mechanics, like in Firefall for example. I guess, Blizzard are too lazy to implement something more, than
this.
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Of course it won't work with current World Quests, that are designed around being the same for all players. But Blizzard can implement new system, that will be designed around having different personal quests. For example you can do as many quests per day, as you like, but you will get only one reward per X hours. Remember? Raid lockouts work the same way now.