If they are going to change AST to a direct healer like the WHM, it's going to need a huge rework. All of the healers are in pretty dire need of one, including whm in my opinion. For several expansions they've taken spells away from WHM only to give them back at a higher level combined with some other ability they took away. They really don't seem to like/know what to do with healers... and the new Sage job does not look that impressive. They need to make healers fun to play and right now... they're really not and they are painful to level through the main story quests.
I suppose the DPS class I'm most interested in seeing what they do with is Summoner.