Tattered Dreamleaf

Recapping the experience as someone who helped out:

1. 
   
2. Obtain this quest by someone sharing it with you during a superbloom (I was in a raid group)
3. 
   
4. Complete the superbloom (opening all three bags + boss = 100% quest completion)
5. 
   
6. Leave the raid group, get invited by the person wanting the buff
7. 
   
8. Regroup with that person, complete the quest (Ohn'ahran Plains) and get the quest item (Restored Dreamleaf)
9. 
   
10. Use the item on the person with the legendary
11. 
    
12. Feel good about helping out a fellow player
13. 
    

Once you receive the buff it will be lost when you logout or leave group, but this is just a visual bug, the buff will remain active. After doing the quest 4 times I was receiving 20-30 Dreamleaf per bag.

The reward from this quest can be cast on yourself. The quest itself isn't repeatable so I have been getting guildies to do the quest and grant the buff.