Ysera's reduces the amount of mana you need to spend, and you really don't need the whole raid at 100% hp. If you are topping the raid off CW will be equally useless and I can't swiftmend off of CW. I don't think I'd use CW in any spec. Renewal is useful on low damage fights with big burst phases for dps, I could just bank my dream of cenarius procs as feral though and moonkins can heal themselves. I feel like as a tank I'd almost always take YG for the constant healing stream and use my other CDs to mitigate incoming damage.
Ok, lets look at the resto druid instant cast arsenal that he could be using whilst running.
-Swiftmend
-2 Piece, HT
-NS, HT
-Barkskin
-Ironbark
-Mushroom Bloom
-Tree Form: Regrowth (if specced of course)
Your druid has SO SO many spells he can use in combination to keep himself up, not to mention rolling lifebloom/rejuv, as there is only a minor mana downside to changing lifebloom target.
Ysera's over the course of a fight will have saved me enough mana to use that regrowth on myself if need be.