Im going to keep the patch changes in mind where we will return to 100% raid healing. 22-24k mana is ideal and around 275-300mp5 should be plenty with replenishment.
My overall consensus for every encounter is haste haste haste haste. Haste lessens the need for spamming chain heals. Lets you choose your heals wisely and allows for mana regen in between casts. Currently there are really only 4 fights that are a remote challenge for a healer so ill comment on those.
24k mana over a 3minute fight is enough if you have replenishment. Currently spamming CH that entire fight with 717 haste and literally go oom the last heal before he dies.
Not hard but in terms of gear you want to get your crit nice and high. CH is useless except for the occasional heal on melee or ppl chaining frost blasts. Its a lhw fight only and if ur on the raid you should only be doing this and riptide of course.
Focus Target frame is your friend. Again haste haste haste. You should just spam your chain heals on the focus target frame and when he changes target find that target on ur grid/raid frames and throw a chain heal their way. The chain heal should land rght after that person gets hit and you will get very little overheal and extreme effectiveness. 2 sec chain heal is all you need once you've obtained that haste wear some more regen. Theres time to regen while your vortex'd and the 2nd phase is more of a spot heal/reaction heal game again allowing regen. Save your mana tide for the 2nd phase as its a good chance your healers will need the mana then.
Sarth 3 drakes
Go for haste to get quick heals off. With the bursty nature of the damage in this fight you'll want as much as possible. Favor single target healing on the raid and chain heals on the elemental/drake tanks to help out melee. If you're not on the drake tank you should be able to position urself near the main tank. Throw riptides/lhw their way and its also great for moving left or to the middle for lava waves.
Its not a massive raid damage fight when executed correctly and if your planning on getting sarth down with 3 drakes you shouldn't have to do a huge amount of healing. Mana is very rarely and issue and you will have time for 2 mana tides so get your first one down quickly (around the first or second drake)
The best advice I can give to shamans healing 3 drake Sartharion is that you want to have most, if not all, of your mana pool whenever Vesperon lands. If you can pull this off (not stomping on druid hots, intelligently healing with LHW, Riptide), then you're set for near-spam chain heal with some MT support until Shadron is dead. My goal is only to have my mana pool hold out until Shadron is dead, and at that point you should start to use less mana than is being returned to you (assuming your dps gets the acolytes down in a reasonable amount of time).
More on topic: I don't think you need to lean your stats one way or the other for any fight. The fights described above that pose a significant healing challenge will require you to use just about everything (and if you aren't, you're wasting mana and/or time). Going with tier gear gemmed SP/Sp + Int/Int + Mp5,SP+Stam (Red/Yellow/Blue) will give you a very good stat balance for any encounter. The tipping points in your gear are your trinkets and weapons.
You pay for the whole chair, but you only need the edge.
Thanks for the input from everyone so far. It looks like conventional wisdom is saying that Chain Heal throughput is best for Drakes and Malygos. There have been caveats about having a certain level of mana, etc, but I think that's probably one of those situations where you're geared enough for the fight or you're not. I'll be editing the original post to include those two fights.
As always this is still up for discussion and I encourage anyone to correct flaws/omissions to make this better.
Having done everything but 3drakes atm, I just have 2 regen trinkets and 2 output trinkets. Switch between them depending on fight and keep the rest of my gear fairly balanced. I'm pretty all over the place with heals on most encounters though, switching from rip/lhw to chain heals and healing whomever unless it is 3drake tries. Post patch I'd probably just go with a haste+mp5 set since we will probably become much more raid-healing centric.
Are we talking about 25-man 3 drake sartharion or 10-man, because I see a HUGE gear change between the two. With 25-man, gear for haste for raid healing sure. 10-man basically means 2 healers: one on the sarth tank and one on the drake tank splitting everything else. At that point (imho) you want to gear for single target healing (crit and spellpower) to keep the welp/sarth tank alive. Raid healing is a bit of an afterthought and something you have to split with the other healer while you have time if that makes sense.
Is it me or does this entire topic basically boil down to: gear for the role you'll be playing on a particular encounter in your particular guild?
If you're predominantly tank healing: wear your crit gear.
If you're mostly assigned to look after the raid: wear your haste gear.
If you don't have replenishment in your raid: wear your mp5 gear.
The best advice I'd give is to take all of your gear, starting in throughput gear with no mana buffs and see how likely you are to go oom. Once you know that you can regear and buff accordingly.
Really, though, given the strength of an IWS + LHW Glyph resto shaman at tank healing and the incredibly diverse nature of guild composition and raid strategies it's impossible to state categorically "you should wear gearset x on fight y". You should ensure you have the depth of gear to be able to cope with any potential role you could be given, such as that day when none of your holy paladins log on and you have to use your resto shaman as tank healers on Sarth+drakes.