And what exactly is that dramatic impact in your play if I am flying? I play on a PvE server, world PvP is not relevant here. Resource nodes will be shared to some degree for members of the same faction. Rares and important quest mobs have shared tagging. And even without flying these would have been equally a problem.
Do you remember TI and how fast all the rares went down there, because of people overgearing them, or the same thing in Tanaan before flight? If anything, flying helps you get faster to this rare which is already in fight. With flying, you get precious seconds to arrive just in time instead of seeing this rare drop dead before you can do anything.
Sorry, but all of this is very subjective. And when things get subjective, then a win-win-solution should be the aim. I am ok with earning flight, but I am not ok with having to wait to a later content patch when by earning all the achievements I have already shown that I have done all relevant content in the world on the ground.
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No, WoD was even worse in this regard. It was designed specifially to let us waste time while on ground mounts. Of course has flying trivialised travel in Draenor, because before flying all zones were designed as mazes. Just like in a supermarket which tries to lock their customers down to spending as much time as possible in the store running around.