Hello,
I'm crazy enough to leveling a lot of chars aiming to get the "Stay Classy" achievement to my personal guild.
I have 3 'main' accounts, and I'm using one as booster, and the other 2 with that many recruited accounts.
I've noticed that after 6.0.2, while dungeons kills and quests seems to give less xp (but this could just be a biased perception from my side), completing them gives now a very large amount of xp. For example, pre-patch I got from lvl 10 to lvl 19 and 85% (full heirlooms, RAF group and the - now gone - Fast Track) by running Ragefire Chasm 5 times. Now, I reached lvl 22 and a half in just 3 runs.
Likewise, on another team, I had to run 1 Hall of Stone, 1 Hall of Lightning, 1 Utgarde Pinnacle, 2 Blackrock Caverns, 1 Throne of the Tides, 1 Stonecore, 1 Vortex Pinnacle, 1 Lost City and the Crucible of Carnage (*) to get from 78 to 85 (*). Post patch, it only took 1 Hall of Stone, 2 Blackrock Cavern and 1 Stonecore.
I couldn't find anything about that on the Release Notes, so I'm looking for any info... expecially if it's meant to stay

(*) I know my routine isn't super efficient, but I get bored really fast Also, until now XP from dungeon quests was really worth it.