If you're a Resto Druid, you should have some kind of a mod to help you with your HoTs. Druids are the king of HoTs, and knowing how to use them effectively is the key to keeping your party up in heroics or raids. Don't discount Lifebloom, because once you have a 3-stack up, it's the most efficient heal you have, since refreshing it maintains all 3 stacks. It's very important to keep both that and Rejuv up on the tank, and to also use Ironbark on him whenever the fight will last more than 12 seconds. In a burst situation, or after the pull is over, you let Lifebloom fall off and do its big finishing heal, or use Swiftmend if you need the burst right now.
Other than that, use Nourish to top up folks who take a single spike of damage, or Healing Touch if it's a big spike. Other strategies depend on the encounter. I'm not a big proponent of Regrowth, except to try to proc Living Seed. If you know there will be AoE damage, set down your Wild Mushrooms in advance and then hit Bloom when the healing is needed. (If you don't bloom them, it doesn't consume any mana!)