This is a matter of the best bad decision. The complaint is that people were out-leveling the zone long before they saw the conclusion to the story. I ran into this multiple times when leveling in Legion and with new characters in my last foray into WoW. It is not much fun when you abort a whole bunch of quests in a zone because they offer you no experience gain. While some people may like that, I think that most players dislike doing quests just to see the story. The general thought was that most players preferred (and Blizzard seems to agree based on this decision) to let the level scale with the player. In that way a player can continue to play through the story AND advance their character at the same time.
Also, fighting level 49 mobs with a level 50 character is not much of a challenge. You should be face-rolling those mobs 3-5 at a time even with a holy priest.
