Here is a rundown on what I do in particular for each boss in Ulduar now that we have most regular-mode stuff on farm. If anyone has any more tips or corrections feel free to add them, I know a lot of us disc priests are the only ones in our guild and probably don’t get a chance to communicate with other disc priests too often on strats 
Razorscale – Focus the boss and bubble whoever gets targetted for the flame stuff. Run around a lot so you don’t get hit, this is a good fight to optimize our instant casts. If you’re on the raid, bubble and penance – since there is no raid wide damage you can afford to throw penance on whoever’s taking damage. On tanks, it’s pretty easy healing. DPS during the first ground phase unless you’re afraid you’ll have mana problems (I pop shadowfiend too so I got into p2 at full mana and he does a little dps!) For phase two it helps to blow Pain Suppression on the tank if it takes them too long to switch to the 2nd tank. or if you’re having trouble staying in range (my tanks seem to like to kite her ALLL over the place)
Ignis – I always have one of two roles. 1 is MT healer, 2 is slagpot/OT healer. MT heals, there is nothing special about this fight. Bubble who you can before and during flame jets (and remember instants can’t get you locked out, so go to town), and giggle when you cast penance and swing around to wherever the MT is tanking Ignis. On slagpot, bubble, penance and a few flashes is more than enough to keep anyone up. When there’s nobody in slag, get a feel for how often he casts Flame Jets and start casting bubbles about 10 seconds before if you can. Prioritize clothies. If you time it well you should get about half the raid bubbled before the last tick finishes.
XT – Personally I think Disc shines more on this fight in 10 man than in 25, where you can tank heal and bubble everyone for tantrum. In 25 you’re usually glued to the tank more than some other fights. If you need to bubble the raid before/during a tantrum because of bad raid damage, PS the tank. Bubble + PoM on someone with gravity bomb is also a big help (like on Grobbulus). I have personally never been assigned to the raid during this fight but it seems like bubble bubble bubble
Assembly of Iron – Disc does AMAZINGLY well on Steelbreaker. I personally overheal like crazy, using penance every cooldown despite the tank’s health, to keep DA up as much as possible. If you’re on fusion punch dispel duty, try to time your bubbles so there is a fresh one right before you start spamming dispel (not really plausible by sheer timing, so I sometimes leave WS off the tank for a few seconds if I’m expecting fusion punch and then bubble right when he starts casting). The other thing I like to do on this fight is bubble people who get stuck in the middle of the Rune of Death or whatever that the runemaster drops, to give them a little more time to get out
Kologarn – Tank healing this is nothing special, but I often get assigned to people who get snatched. Bubble them, penance one, PoM, and flash the others, and if your raid is good they’ll be out of the arm by then. Besides that, get as many bubbles out as you can before Oblivion. Unlike XT and Ignis, this is an unforgiving fight for disc, because if you’re not reactive your bubbles are pretty useless (their raid damage ticks while Kolo’s is one big shot). If you have a lot of haste or a haste set, this is a good fight for that because you can help heal the raid post-bubble-explosion.
Auriaya – blow PS on the pull, to whoever you’re assigned to. Besides that, I have one awesome hint if you’re low on shamans and high on priests — Have your priests rotate fear wards on you, bubble yourself for BT and mass dispel when she casts her fear. It’ll basically be instant
Hodir – Hodir is possibly my favorite fight in Ulduar. As disc, you don’t need to worry about getting the buffs as much as other classes because shield is going to be like 90% of your healing. I have one major goal in Hodir: Keep Frozen Blows from proccing on the tank. A bubble and hasted set of penance/gheals right when he pops it will guarantee this doesn’t happen. Besides that, jump CONSTANTLY unless you’re in a haste spotlight and throwing super fast heals on the tank, and bubble the fuck out of everyone. You will look like absolute trash on the healing meters but everyone secretly loves you, I promise. Also, despite my TERRIBLE FRAMERATE (2-4 fps on hodir 25) I am always #25 on damage taken, sometimes below people who died early in the fight even. fuck yes.
Thorim – Disc is amazing in the Arena. Bubble everybody as much as you can, spam Holy Nova when the commoners come out to help pad AoE damage, and throw Penances like crazy on people who are focused. The results are more dramatic in 10 man but a disc priest is stll an excellent asset in 25 man arena, especially when your other healers are casting real slow raid heals (wtb resto drood). Save PS for phase 2 when a tank doesn’t taunt in time and the first tank has to eat another Unbalancing Strike :/
Freya – Bubble, bubble bubble. Bubble whoever gets the lightning debuff on the big add. Get as many people bubbled as you can during the small lasher phase. The tank doesn’t take much damage, I usually blow every penance on him, keep WS up, and every PoM and don’t usually have to focus on him too much, so I can help out the raid. Bubbles make a biiig difference when all that shit is blowing up.
Mimiron – CRY. I’m nervous to post my hints for Mimiron because I think we’re still tweaking our phase 2 strat. We’ve downed him I think 4 times now but he’s still way harder than I think he needs to be. Another fight of bubble spamming though, lol. Phase 1 is solid for disc, spam shit for lots of DA when the plasma thing goes off — even if healers are blowing cooldowns your tank could still get gibbed without max heals. For phase 2 right now we usually have each priest heal their own party (…yes, we have that many priests) which is hard on me because I am more effective at “o shit” raid damage than “gotta keep sustained PoH going on my doods,” but I manage pretty damn well I think.
Vezax – We use two sets of healers that rotate on the MT, and no raid healers (dps bandages if they fuck up and eat shadow crash). We have one of our holy priests go Disc, and keep one of us in each group. I think I’m still a little mana-wastey on Vez because I’m inclined to overheal a bit to keep DA up, even though I don’t think it’s so necessary. But I have almost 30k mana at this point so I’m not hitting danger zones yet by spamming when i shouldn’t be 
We use a DK tank so Vez stays in one place, and the healers stand on the melee so we don’t get targetted for his bad shit. The big thing about healing here is to keep shield up, and only cast penance when you absolutely KNOW it’s going to make a difference. Nothing sucks more than casting penance when you only needed to flash once, and having the tank take 25k the next hit when your shit’s on CD. This fight is also a good time to use renew to pad the tank if your mana is going alright. Also I sometimes uses penance on the other healers’ rotation if I’m good on mana if damage is really spiky — it’s cheap and instant, why not help?
Yogg — We haven’t gotten far enough on Yogg for me to write anything, hopefully I’ll have something after Sunday’s raid! 
Chillin' in Vezax's room
