I'd love to see more interesting mechanics for healers, though I don't think having a buff (shield) that is physical or magical dmg aligned is such a good idea. I struggled in HW knowing what to use with dark mind and what skills it was useless against. There are too many instances and mobs in game now to reliably be able to remember what to use where and it will only get worse.

My contribution to the the thread is allowing healers to transform/explode their HOT or their shields for a quick burst heal on the target if needed. You could even make that a burst of dmg, or an area cleanse (esuna).