My two cents as a main healer - Dual spec would keep me playing more and allow me to actually quest/farm at a reasonable pace as well as PvP more. I just do not have the gold to sink into respecing 5 times a week to play the game when I also need to spend that gold on enchants, gems, consumables, repairs, etc.
As it sits right now, I pretty much raid log and play other games in between raids.