The eight rares required for the Glorious! achievement, Major Nanners, Yorik Sharpeye, etc, have not really been effected. Every one of them (minus Sahn Tidehunter who moved in patch 5.3) are in the exact same locations as they were at the beginning of MoP. The only major difference you'll notice with them, is that their surroundings got uglied up.
"New" Rares in the Vale:
Before the Vale got all funked up, people working on Golden Lotus rep could get credit for killing powerful enemies at the end of a long arduous line of dailies each day. Although there were sixteen of them, only a few were available to kill on any particular day. All of these powerful enemies were (and still are) required for the achievement One Many Army.
All sixteen of these "powerful enemies" still exist within the Vale, but they have changed drastically. First and foremost, they have been made rare! Well, I should say "rare". Like just about everything these days they are on fairly short spawn timers. You no longer have to wait days to see one either, all of them can (and will) show up every day - yay! It is also worth noting that they will all spawn in during a server restart.
Another important little detail is that many (but not all) of them have moved. I marked all sixteen of these fledgling rares with bright pink stars on the map below. Several of them spawn in caves/underground, and I have noted that on the map as well. If you scroll down below the map, I also have screenshots of each of them in their new locations.
What you get from killing them: