yeah current bug in the game mechanics if you cast something while the cast bar is still filling/emptying whatever you want to call it you can get double the perk.
IE resurge -> innervate 3 ticks -> dark infusion. That is on the fix list though for 1.2 so don't get used to relying on it. Only time I really abuse it these days is WZs....resurge -> DI -> DI. Toss in a recklessness before you DI if you're feeling super nice...2k HP to full HP in under 3 seconds lol
As for the original topic. Here is what I use for a spec:
http://www.torhead.com/skill-calc#201GGrRbd0dGzZf00MZoM.1
A few of the talents are flavor. Empty Body, Dark Resilience, Haunting Presence, Sith Purity, Conspiring Force. As long as the core is there you're doing it right 1% damage reduction isn't a game breaker, and neither is 2% more healing. Just comes down to personal taste.
General rotation. Resurge -> Innervate -> Consumption. Pepper in a Dark Infusion on your tank, a Revivification near your DPS, bubble on those about to take spikey damage (lightning balls at Soa, aggro changes on Bonethrasher) The above mentioned 3 though is your 'goto' rotation though. Obviously you pop a Dark Infusion before your Consumption if you need the heals first or you're not hurting for force, just try not to lose too many of them because that is how you keep the heals coming lol
Fastest burst heal; Resurge -> Dark Infusion -> Dark Infusion (will be a bit slower after 1.2 fix) -> Innervate -> Consumption (or start the rotation again if you need to, just watch your force)
Just before the tank pulls, it is a great making sure he has a bubble (bonus if you can also get your aggro pulling DPS friends as well). As the tank is about to pull or pulling make sure resurge is on him (+10% armor). Make sure you are keeping it refreshed on him. It is a 15sec buff and is on a 6sec CD so you can pass it around a bit if you want to, just make sure tank has it up on him.
Lots of trial and error involved with learning your preferred "feel" just make sure you're not making silly mistakes like casting Dark Heal unless it is a super emergency or something and literally can't wait .8 seconds.
I really haven't toyed with my merc healer too much yet, but Sorcs really are fairly solid all around almost to the point of broken . You can burst 14k+ heals in 5 seconds, keep the entire raid all topped off if they know how to stack up, preventative heals with the bubble, armor buff your tank, if managed properly unlimited force.
Looking forward to playing around with my merc more often now that I have him leveled, but TBH doubtful I would ever retire the Sorc.
EDIT: Does anyone have any stats or a good read on Alacrity for Sorcs? After doing far too much information gathering on the Merc healer I decided I liked it for him longer term, but not sure how the Sorc will like it.