The first thing that came to mind was how to achieve mana efficiency when using my larger heals. As a Paladin, for most of my healing life Flash of Light has been all that's required, with the occasional Holy Light thrown out in emergencies.
After doing some research, I found that downranking Holy Light is the answer. In most instances, a max rank Flash of Light will do, but now and then I throw in a Holy Light Rank 5, which has a slightly lower effective mana cost, and will allow me to keep the Light's Grace buff active in case I need to throw out a big heal quickly.
I've been experimenting with various ranks to see which ones work best for me, but it is definitely something to consider once you reach a certain amount of +healing.
Salud over at The Holy Light posted a great article on downranking a little while back that's well worth checking out if you're interested!