I used to do a ghetto fabulous way of healing, by putting a heal macro on the same as my main DPS key with FTL, and the macro simply targets the targettarget, so whoever has aggro gets the basic heals. This was back when multiple commas would increment once per key press, rather than the current way of incrementing past all the commas until it hits a spell. It was nice to have some "passive" healing without having to do anything.

When I leveled priests, I used smite spec and the healing from that got me all the way to 80 level content without ever having to really cast a heal. And I would often be near the top of the DPS charts, while healing.