Good Job,

I have my 4 alts at ~52 right now with 1 day 14 hours played. I used the boosting method with my 70 paladin though.
I ran them normally from 1-10 (two boxing them).
Then at 10 I ran them through SFK till 20, didn't take long doing it in 4 pulls, reset.
At 20 I took them to SM: Cath and ran them through till around 40. It was a little slow at first because of their level but sped up quickly doing it in 2 pulls and resetting.
At 40 I hit a little speedbump and took them to BRD till 45. It was really slow and if I had it to do over again I would have quested.
At 45 I took them to strat but it was slow also and I decided to try questing.
I took them all to hinterlands and got them all to 48 by doing jinth'alor, the turtle quests and lard's lunch.
Then I went back to BRD since I was high enough for the quests there, and leveled from 48-52 in one night with quests. I only did about half of them and plan on going back tonight, then doing either strat or scholo since they will be high enough for quests.

Questing in an instance with a high level is crazy high experience.