Most people [especially in PVE] use addons or mouseover macros, or both.
Some healing addons:
Pick only one line since these addons do the same thing.
- Grid + Clique (I used this in the Wrath of the Lich King expansion.)
- Vuhdo (note: it's possible to combine vuhdo+clique if you already have bindings set up in clique. I do.)
If you want to bind a click to a spell, then you need an addon to do it (all the above addons will).
Alternately, you can use the built-in raid frames provided by blizzard and use clique or bind your spells/mouseover-macros to your keys if you prefer keybinding.
Also, mouseover macros are not mutually exclusive from addons.
You can use something like clique to launch the macro based on a click+key combination.
You can use any unit frames addon like grid/vuhdo (and probably healbot, elvui, etc.) and I think it will count as a mouseover.
Here's a post on mouseover macros from a prominent healing priest in the wow blogger community, Matticus.