However, I also wanted to comment to some who are posing druid healing strategies of maintaining Rejuvenation and letting Lifebloom pop on the tank... That Lifebloom stack currently ends up costing about 4k mana for a ~16k heal and reapplying 3 lifeblooms takes about 4-5 seconds depending on lag and haste. The better option is Nourish spam on a Lifebloomed tank - Nourish costs ~1800 mana, and heals for about 10k. More importantly, Nourish (and Healing Touch) ***REFRESH*** Lifebloom.
That being said, Rejuvenation is an expensive option right now, as it costs almost 5k mana, but is better in conjunction with Swiftmend(which is free) + Glyph of Swiftmend than other options for additional healing, such as the mana sink of Healing Touch or, Dear God, Regrowth.
As a final note - Please try to make use of your Omen of Clarity Clearcasting. Although it's unpredictable, I find that I'll usually get one at least once every 25 seconds, allowing for a free Regrowth or Healing Touch. It may not sound like much, but during relatively stable combat phases, you can maintain or even rebuild your mana pool by keeping the tank and Lifebloom healed with periodic refreshes of Nourish and making some of their HP deficit up with a Clearcasted spell.
By the way, I still haven't killed that prick. He does 5k shadow damage to everyone every second and you're lucky if your group is at 50% when it starts! It outdamages ToL+Tranquillity! I've even done triple lifebloom stacks on everyone in ToL with Wild Growth. Lowest I got him was 100k. I'm guessing that DPS need to step it up to end it before we run out of HP lol.