Here's the armoury of my char: http://eu.battle.net/wow/en/characte.../Nymsee/simple (Nymzee is my main)
All I'm doing (to heal pretty much any encounter) is this:
HST on CD
RT on CD, roll on tanks + myself (if no 3rd tank)
Mana Tide after first HST then on CD throughout.
HTT when needed, but prefer to time it so it doesn't collide with HST/MTT
Call of the Elementals after using HST during a high AoE phase (midway through Tsulong night etc)
UE + HR together always, generally means I'm using HR every 13-14 seconds.
Outside of the above I either (depending on the situation):
CH or HW
As you can see, I'm sitting at 52% mastery, 11% crit and I have the first haste breakpoint. My spellpower is really low (mostly because my gear is gash). I aim to get the second haste breakpoint when I have more gear.
Basically though, it seems incredibly easy to pull stupidly high numbers. Maybe the PUG healers I'm playing with are just bad, but I seem to be outhealing everyone on almost any encounter.