I've just geared up an alt Disc priest and would like to try healing in LFR for fun, but am not sure what to expect. The only raid sized healing I've done is a couple of Sha of Anger pugs, which were sheer chaos. First time, I went out of mana fast spamming prayer of healing. Second time went better, with more emphasis on shielding and penance. Still, I felt uneasy about what I should be doing: trying to look after 40 people was just too much for my limited mana pool. I suspect LFR will be like Sha pugs with no spoken coordination or healer assignments, so what should I do? A veteran holy priest said disc was better at tank healing than raid healing, so should I pick a tank and focus on keeping her up? The way tanks seem to charge ahead in LFR, I think a dedicated healer or two would be prudent.
LFR is a joke healingwise. Smite, Penance and holy fire is what you do, throw the occasional shield on the tank for rapture if you have mana issues. I usually top HPS just with smiteheal (allthough that doesn't say much). If you want to have some fun and know the encounter, use Spirit Shell before Aoe Damage, but you don't need to.
There's not much difference in healing lfr compared to normal raids, the raid will take less damage giving you more opportunity to dps/atonement heal but that's about it. You can get through lfr by just spamming smite or even putting follow on someone (and tab out and watch some starcraft:P) but if you want to do it properly here are some basics: Make sure to time PW:S usage so you have rapture up the majority of the time, use holy fire and penance (offensive) to build evengalism stacks (and use archangel on cd or when the healing is needed based on the fight, don't hold for it too long). Use atonement+heal/gheal+pw:s for general tankhealing, PoH+pom+cascade for raidhealing. Make sure to use and stack spirit shell (preferably with archangel and/or PI as well)+PoH when you have predictable raiddamage coming out. There's a lot more to playing disc properly but that should be enough to get you started.