I realize you're proud of your long post, but your profile tells us who you are.
Ok let me preface this by saying my guild is doing 2 ten man Ulduar groups and one 25 man. We are making steady progress and having blast learning the boss fights in 10 man, and have not gotten very far yet into 25 man. We have found the online strategies for some boss fights to be very sketchy in many cases, so we are reading, watching videos, but relying on our own experience to change our strategy rather then sticking with what someone else had success with.
I am surprised nobody here is suggesting that priests pop Guardian Spirit on the pull if you expect the MT to take a ton of burst damage early in a fight. It not only prevents him from going down and brings him back to 50% health, but it also gives a 40% healing bonus to any other healers hitting the tank during its 10 second duration. I have completely changed my mindset on Guardian Spirit from it being a "Oh crap save the tank, or myself" button to where and I pop it early on fights I know tanks will take a huge amount of burst damage on (25 Man XT-002 for example). When the cooldown comes back up I use it as an insurance policy to keep myself or the MT up if I want to break from healing to do some mana regeneration for myself and the raid.
Mana regeneration: What is the best way to take advantage of our talents to get the most out of mana regen? A Guild mate who is a Disc/shadow priest pointed out a great combo to me. Pop your shadowfiend just before you pop your hymn of hope your base mana pool is increased by 20% temporarily. Since your shadowfiend regenerates mana based on on your total mana pool you are not only getting mana back from your Hymn (Cast this when you are very low on Mana to assure it hit you), you are getting a 20% bonus to your shadowfiend mana regeneration for up to 8 seconds AND getting a ton of mana regen back to 3 other casters in the raid to boot. If you are having problems with going OOM as someone early in this string was indicating, this is a winning combo. If you are in a fight where you are in danger from getting taken out by burst damage or losing a tank to burst damage then after you top yourself or the MT off take a break from healing for 10 seconds by popping your guardian spirit on yourself or your MT send your shadowfiend then start channeling Hymn of hope for uber mana regen and insurance policy to make sure you or your MT don't go down while you are not healing. Essentially its a nice 10 second break (Duration of guardian spirit) from healing to get mana back so you can kick back and take a sip from your cold beer while you wait 8 seconds for your hymn of hope to end without worrying about yourself or the MT dying. If no other healers are healing you or the MT during this process and you take 150% of your health in damage and die in an 8 second timeframe, then chances are you probably would have died even if you were healing..heheh
Essentially i have found that guardian Spirit is a really amazing tool to use as a healer as anything BUT an "oh crap" button. Mainly because I have found that often times when i see a tank going down, and I try and hit the button well before i see his health hit zero I find that lag from either the server or client has the tank dead and me cussing and whining that "#%@#^ I hit guardian spirit before you went down, WTF". Then to further add insult to injury my guardian spirit wings pop on my toon to just show everyone that I not only failed to save our MT, but I have also just wasted my guardian spirit spell (Because I use spell self targeting if I am not targeting someone/something).
It doesn't happen 100% of the time obviously, but I'd say about 25% of the time I have used Guardian Spirit as an "oh crap" button to save a tank while I could still see a health bar, the delay from my button push to it registering and going off the tank dies, 75% is not a good success rate in my book. In using guardian spirit the way I do now i help the raid with mana regen and prevent a tank from going down early in the fight so i am using it just like any other cooldown, and rarely as an "Oh crap" button.
Atheldane - Ravenholdt lvl 80 Holy priest - Dark Guard
P.S. Our guild is taking down 10 man kologarn easily at this point but I am nervous that we may not fair as well this week due to the 30% reduction as of todays patch to the heals for divine hymn. I used Divine Hymn to get through one of the early oblivions or to help keep people in grip and group up, but with the nerf to that spell as of todays patch I am curious to see any suggestions for that fight now that we will be doing 30% less healing? Does anyone get through oblivion and grip with anything but PoH and CoH spam plus a shield to whomever is gripped??