This is a minor bug that affects both the XBOX and PC versions of the game: it disables the requesting of Mystic Focus accessories for all leaders (they will request Balance Focus ones instead). Although we call it a bug it's also possible that this is an intended change after playtesting the game.
Normally, leaders will request accessories from the party inventory based on their current focus. The default focus type is Balance, the two others are Combat and Mystic. The accessory types that will get requested are pre-set for each focus type for each character. However, due to a bug in the game code, the loop that checks the accessory types requested for each focus never actually checks the Mystic ones, but defaults back to the Balance types instead.
Since there are no patches in sight for the game, the only way of fixing this issue is to manually edit the game executable. The following information is provided only for the PC version of the game.
WARNING: THIS ARTICLE DETAILS METHODS FOR MODIFYING CRITICAL GAME FILES. CREATE BACKUP COPIES OF ANYTHING AND EVERYTHING YOU PLAN TO EDIT BEFORE YOU BEGIN EDITING. UNDERTAKE MODIFICATIONS AT YOUR OWN RISK.
Fixing this bug requires a simple Hex editor, and the change of a single byte in the executable TLR.exe. The byte is located at address 010B3030 (hexadecimal), and its value is 02. To fix the bug you have to modify this byte to 03. All leaders with the mystic focus should begin asking for mystic type accessories as soon as you have any that are better than their current accessories.
While this may not be apparent at first glance, fixing this bug will cause the mystic focused leaders to use Rings and Necklaces instead of Amulets/Anklets and Bracelets, which are usually the Balance type accessories. This can cause them to have significantly less HP and/or AP/SPD, which may not be part of the desired result.