With the new patch, you can cast healing touch from tree form, it simply changes you out of tree form.
However, I've found with an adequatley geared tank, my Rejuvenation + keeping lifebloom stacked 3x usually keeps the tank up NP. I dont neglect Swiftmend, as its a powerful ability on a 15 second cd. IF I need a stronger heal, I simple cast regrowth, (with talents =67% crit rate) so it is a fast 3.5k heal.
The exception is of course boss fights, where I -->somtimes!<-- have to use Swiftmend or Natures Swiftness, more often I find myself hitting tranquility for the full party heal.
As a resto druid, you will find you top the healing done charts, or close to it in most raids.