Cause, I don't know if I should spend time trying to get it, as I'm just level 78 atm aswell, I doubt I'll have enough time.
My advice is to pick up the quest and just start it. If you get the cloak before 6.0 is released then good, you got some good achievement points and experienced the main story line of MoP. If you dont get the cloak then you have not really lost anything anyway.
they've also implemented a lot of catch up mechanics for the legendary quest line.
Since this is apparently the last patch before the new expansion pack
this might be the last raid content patch but there will be another patch before the expac drops