I would suggest SE lean heavily on adding party support the Healers. Its a method to help the raid to increase their DPS without require healer to actually DPS. It helps make healer jobs more unique. And it helps make healer job interactive.

SCH
Give Selene debuff style abilities. Lower recast timer on fairy abilities but make the fairy gauge the resource to use those abilities.
Add Libra that would increases target's damage taken by 2-3%
Add Fey Wind type buff when Seraph is called; reduces weaponskill cast time and recast time, spell cast time and recast time, and auto-attack delay of self and party members by 3%.

WHM
Give direct buff spells like Berserk which increases Damage Dealt, Haste which reduce cast and recast of weaponskills and spells, Slow and Blind. Classic White Mage spells.

AST
Change the cards to buff jobs rather than DPS. This would be helpful all around rather than a small portion of the game. MND, DEX, STR, INT, Tenacity would be the best options to do this. Ewer can restore MP and add a passive 1% Crit Rate to all cards to off set the chance the job/card combo isn't available.
Keep and adjust Divination as it currently is.