If Theurgists are having trouble completing your level 48 Life spell quest, you must have completed a sidequest in MooShu in order to have access to Oakheart in the Jade Palace.
You must complete these quests, in this order, to get to Oakheart in the Jade Palace. A lot of these quests are the same side quests that you need to complete for the “Wizard Tours” quest or Obsidian Chests quest to get access to the one chest in MooShu.
Cave of Solitude 1. I’m Cursed (from Mossback) 2. Rock On (from Mossback)
Kishibe Village 1. Wear Your Gloves (from Mossback)