One thing that I always like to tell party members is to understand how grandiose Prayer of Healing is.
Prayer does everything in a big way.
It heals the most out of all your spells.
It leaves vulnerable for the longest time.
It has the highest HP/Mp cost.
It has the second highest range of healing spells.
The important part is the range. You don't need to stand as close to the healer as you would for Light of Healing.
Yes, a thank you is necessary to all players who are paying attention and trying to help out their healers by not wasting their heals.
Get away from me.
You can stand next to your healer or you can stand far away. You're still going to be in range of Prayer's healing. The difference?
If you're near your healer, and monsters are coming after you, wouldn't that also result in the monster being near your healer as well?
Which by the way, is not good.
Also, don't use your healer to backdrop a monster's attacks. If they run up behind a monster and cast Prayer, there's a good reason they're behind the monster.
Most monsters work with frontal attacks. By staying behind the monster a healer is usually safer and has less chance of being interrupted.
Some conscientious players interpret Prayer the same as Light of Healing, and move next to the healer. Doing this turns the monster around so that it's facing your healer. That means any longer ranged or piercing attacks hit not only you, but the healer standing behind you as well.