I know Flash Heal is most probably the best option, it's quick, benefits from the talents in the disc tree and is probably the way the developers want Disc to be played. It was more of something i wanted to attemt. I gave it a shot in VOA last night, not really much of a test since that place is a breeze anyway. I did however find that Greater Heal just generaly feels very horrible to cast. Flash Heals can be cast really easily on the move, where as with Greater Heal, i feel i have to set up camp to cast it lol.
So i'll probably end up sticking with Flash Heal and possibly throwing a couple of Penance > Greater Heal combos with the haste from the shield.
It is nice to discuss these things though =)