So Ulduar is rough. Not hard per say, just rough.
We brought a few trees to the raids, all different specs. Here's what we learned.
#1. Living Seed is garbage. Pure and simple. Those points are better spent elsewhere. We opted for Celestial Focus. It accounts for less than 3% of our healing. 3% haste is better.
#2. Revitalize is best on melee. This means WG is best used as a melee heal. You are guaranteed to hit 5 people, unlike ranged, who, when spread out, will net you maybe two.
#3. Nature's Swiftness is better used with regrowth than with healing touch.
#4. Rejuvenation is our most effective heal. Its cheap, fast, and with the glyph, very effective.
#5. Lifebloom is great for MT cushioning and to net you some mana when you really need it. Not much else.
#6. Nourish is great, but with all the direct healers in the raids, it mostly goes to overheal anyway.
#7. HoTing the MT, WGing the melee, and using Rejuv as a raid heal, popping SM when needed, puts a druid at the top of the meters. Easily.
#8. Here it is boys and girls. The numbers are in. the mana regen nerf is... a joke. Seriously, specced as I was for longevity in 3.0, I now finish fights with 60% mana still. That's mana that could have been used for SP.
So, I did what any reasonable tree would do. I dropped my beloved spirit. I replaced ALL my +spi gems with either Runed Scarlet Rubies, Luminous Monarch Topazes, or Purified Twilight Opals. Reenchanted my gear for SP, except my weapon, which is still Spi, because the mats are expensive and I is need money. Need to swap my Spirit World Glass for the Mortal Egg, sadly, but we're talking NO mana issues.
The biggest mana strain we encountered was the healing on Ignis the Flamer and that's with Brezes and Innervates going to other people who got meleed on their way to the slag pit. Still, we're talking 40% left over mana. No pots, no innervates.
Here's another secret. Ignis the FlameBroiled Whopper, is by far my FAVORITE healing fight in the game. Hands down. Its just so, hectic and fast paced, so much going on, so many people needing heals, moments when you can't heal, getting sent to the slag pit, RAWR!
My advice, go back to the BC mindset. Spirit is out, SP is back in. But don't forget to stack that int.