Granted, ranger is down there with BL for weakest healers. But when it hits the fan, it's often my heals that make the crucial difference.
The shaman is frantically slowing adds, tank is getting as much aggro as possible, other ranger is TMing, cleric is healing the tank and the druid is healing the other ranger, and I'm spot healing the shaman, druid and cleric. A little crazy, but it happened a couple times. I let myself die once after a bad pull, but no other deaths in that group in the 5 or so hours.
I may be a ranger, my best heal may have a base value of 428, but I'll not rest til I get Improved Healing!