Can taste the bitterness in your post.
OT: They're taking it out because it's no longer relevant and neither is the item that it created. The fact that the item in question was so accessible during the current xpac means that anyone who wanted it, has it, or at this point is very close to having it. There's no need to keep the reward in the game after that.
That being said, i do agree that keeping the story in somehow would be awesome. I did like the MoP quest line (didn't much care for the cloak as a reward, or the ring - i'm not a HUGE fan of everyone getting everything for nothing- just my own preference of course).