As Toxigen said, JBB isn't necessary for any endgame content.
I still use mine at 60, JBB isn't just for powerleveling. Saving spell slots is always very nice on a Shaman.
https://youtube.com/watch?v=umuVBewCNgY - An example of using JBB on Cliff Golems. I did 5000ish damage with JBB, which is 1/6th of it's life.