I was also running out of mana on my resto druid. The problem was overuse of rejuvenation. So I changed my heal macros to these, and haven't had any mana issues since.
#1 (mostly for tank heals)

/castsequence reset=target lifebloom, lifebloom, lifebloom, nil
/castsequence reset=target regrowth, nourish, nourish

#2 (more like the oh shit button, since Nature's Swiftness + Healing Touch probably isn't worth talenting).

/castsequence reset=target rejuvenation, healing touch, healing touch, healing touch, healing touch
/cast swiftmend

I use both of these on my mouse with Vuhdo, and spam Wild Growth along with my dps.