Keep Joyous Journeys active permanently. People returning for MoP will actually want to level alts. Keep it active up to 85 so after that when you start leveling in MoP it isn’t active.
(If you kept it active till 90 I wouldn’t be made too though)
Jj will not be needed at the release of MoP they do another xp squish from 1 to 85. It will take a day to level in heirlooms.
Joyous Journeys was fine, and I got a good use out of it, but Discoverer’s Delight is way better. I say bring DD to Classic Cata
Why do Classic players hate playing the game so much?