The 3.1 patch comes with a total new healing style for druids. These changes include: spirit changes (reduced regen out of combat & reduced mana gained from spirit), the mana cost of lifebloom was doubled unless you let it bloom, nourish was buffed through a new glyph, and the Nature’s Grace is now a buff that lasts 3 seconds.
The new druid tank healing style will be to get up your HOTs (regrowth, rejuv, 1 lifebloom), and then you’ll cast nourish until you need to recast lifebloom or your other HOTs. To make nourish-spam good, you need to either have the T7 4-piece bonus, or you need the new nourish glyph they are supposedly giving inscriptionists in 3.1. If those bonuses stack, then having both is recommended for now.
The most mana efficient way to heal with this is to always let lifebloom fall off if there is a 3-stack on the target, and then you don’t want to waste 3 GCDs in a row putting it back up, so you may wait and put up the 2nd when the first is about to fall off, and the 3rd right when the 2-stack is about to fall off… and then let it bloom once you have 3 up. During this whole time, you’d be casting nourish and refreshing rejuv/regrowth HOT as needed.
This pretty much completely standardizes druid healing on tanks.
For AOE healing, it’ll be wild growth, rejuv, and maybe single lifeblooms. It would probably make sense to put the regrowth HOT on the tank, but throwing it around as a raid heal will not be sustainable. You can, however, sustain using wild growth & rejuv/swiftmend as your raid healing arsenal. I’d recommend single lifeblooms if the raid is taking enough sustained damage that you think the bloom would likely heal them. If you don’t like using nourish, then make sure you get put on raid healing, as nourish makes a poor raid heal (since you need stacking HOTs to make it good).