World of Warcraft: Cataclysm brought with it a brand new world filled with interesting stories to unravel and unique quests to solve. While all of that sounds like a great idea on paper, in reality it was a ton of wasted effort as players quickly over-leveled the content and then abandon it half-way through, thus never really experiencing the zones as they were intended.
With that in mind, I am very glad to say that the latest Update 7.3.5 has implemented Legion's level scaling system to every single zone across every single expansion! So if you ever wanted to completely skip Outland and just continue questing in the Eastern Kingdoms, you now have the option to do just that. And more importantly, visiting dungeons while leveling no longer means you have to abandon half of the zone you're currently exploring due to over-leveling!
Besides the changes to level scaling, Update 7.3.5 has also brought with it a new end-game storyline set in Silithus, a brand new Battleground by the name of Seething Shore, new Legendary items, balance changes, and Personal Loot for all dungeons. Whether that last change means it's going to be a lot harder to farm for Transmog gear in old dungeons, I'm afraid I don't know, but it should at least make dungeon runs a lot more rewarding outside of the end-game.
If you're interested in all of the details, as well as the full patch notes, you should head over to the official forums. Have fun with the new questline!